Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/1102592.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      F/M
  Fandom:
      Star_Trek:_Alternate_Original_Series_(Movies)
  Relationship:
      Pavel_Chekov/Leonard_McCoy
  Character:
      Pavel_Chekov, Leonard_McCoy
  Additional Tags:
      Genderbending, always-a-girl!Chekov, Menstruation_Kink, Alternate
      Universe, Medical_Kink, Mildly_Dubious_Consent, Oral_Sex
  Stats:
      Published: 2013-12-26 Words: 2021
****** it's cute in a way ******
by mr_charles
Summary
     Polina's biggest shame is McCoy's biggest turn-on.
     (or the one with the underage and the menstrual kink)
Notes
     title from she wants revenge's "tear you apart"
     un-beta'd and all mistakes are mine
     I welcome corrections if anything is off
See the end of the work for more notes
It happens when Polina is 15. She goes with a few classmates to a party off-
campus and ends up in a back room with an older boy. His kisses are too
forceful for her liking but she likes the way his blonde stubble rubs against
her neck and the throaty way he groans her name. His fingers are cold as they
trail up her pale thigh into her skirt and before she can say something, he
jerks away from her. His mouth is turned in disgust.
“Fuck! Were you going to tell me that you were on the rag?” His fingers are
smeared with red.
“I…” she starts, absolutely mortified. It’s early she wants to say but he’s
already out and slamming the door behind him.
The stares and whispers follow her on campus and in class but by the time her
next cycle starts, the chatter has died down and the gossipers have found
someone new to focus on.
 
She avoids boys for the longest time. It’s not hard; she gets assigned to the
Enterprise, gets to wear a gold dress that’s too short in her opinion, and
nurses an awkward crush on the captain. But life is good for Polina Chekova.
She takes the regulated hormones that Nurse Chapel gave her while she was still
a student. She only gets her cycle three times a year, which is great if you’re
planning on being in space for five years at a time.
(she wonders briefly if she can stay on the pills forever; she never wants a
repeat of the Party Incident)
One night, or technically early morning, she’s up in her quarters writing
letters home to her family. You should be in bed, Polina she chides herself as
she finishes up a fourth letter. Her pen skitters across the paper as a sharp
pain shoots through her lower abdomen. She cries out in Russian as it throbs
through her; like cramps only magnified over a hundred percent.
In her sleep shorts and thin tank-top, she stumbles to the med bay, half
convinced she’s dying. It’s her appendix, probably. Or her stomach has burst.
Or it’s her stomach and her—
“Ensign!” Doctor McCoy startles her. “What are you doing here this time of
night?”
“I…” Polina swallows. “Is Nurse Chapel here?”
“Just me, kid,” he says, eyeing her warily. “What is it, ensign?”
“It’s, um, a feminine matter.” Her voice is low and she’s staring directly at
the floor.
With a raised eyebrow, he points her to a small exam room. “There’s a gown in
there. Someone will be in there shortly.”
As she closes the door, Polina is thankful the gown isn’t paper. Goosebumps
prickle on her skin as she realizes she didn’t put her bra back on before she
left but as she pulls her shorts off, she realizes that her lack of bra is the
least of her problems.
The crotch of her shorts is soaked through and sticky with blood. Her panties
are in the same situation; both are probably ruined. Panic surges through
Polina, a constant stream of no no no no no noas McCoy opens the door.
“What happened?” His voice is rough and Polina tries not to cry.
“Nurse Chapel gave me the pills and the pills worked and I only bled every four
months and I—“
“Shit.” McCoy is scowling now. “Ensign, how long have you been on those pills?”
Polina tries to remember. It was shortly after the Party Incident and her 18th
birthday is in only a few months…
McCoy takes her silence as ignorance. He swears under his breath. He gestures
vaguely to the cupboards behind her. “There’s some…stuff…in there. Clean stuff.
Clean up and let me know when you’re decent.” He shuts the door behind him.
Polina sobs and curses as she pulls the smallest pair of generic cotton panties
out of the drawer. She uses wet paper towels to wipe the worst of the mess off
her thighs. There are even smudges on her knees. The small pads in the bottom
drawer seem like a ridiculous option considering her situation but they’re
better than nothing.
Kind of.
“Doctor?” she says, poking her head out of the door. She sounds like a scared
little girl. She’s wrapped herself in the faded blue hospital gown. McCoy looks
torn between pity and annoyance.
“Lay down, Ensign.” Polina situates herself on the hard cot, flushing red. “Are
you sexually active?”
Polina shakes her head. “No, Doctor.” She gasps quietly as McCoy presses his
gloved fingers lightly into her lower abdomen.
“Why are you on birth control?”
“My periods,” Polina says. “I… I don’t like them.”
“Unfortunate academy gym class incident?” he snorts, looking at the scanner
above her head.
“There was a boy,” she says before she can stop herself. “He wanted to but I
was bleeding and he… made fun of me.”
McCoy frowns, a look of confusion crossing his features. They’re nice features,
Polina thinks, as he scans her. “Ridiculous,” he mutters to himself. “A real
man should be able to appreciate a woman. A real man should appreciate all of a
woman.”
“Doctor?” Polina asks, not sure if he’s talking to her or not.
He snaps out of his reverie and clears his throat. “No more pills. Not until I
say so. Your reproductive system is all shot to Hell and needs a good six
months to reset itself.” At the panic in her eyes, he says, “You won’t bleed
like this constantly. I’m going to give you a sedative and have you spend the
night here so I can monitor you overnight. Is that alright?”
She nods quickly, panic turning into dread. What if, in six months, she meets
someone? What will she do then? Tell them to come back in a few months? A quick
injection to her neck has her settling back into the cot, eyelids fluttering.
Her last thought is of the doctor covering her with a blanket.
 
Polina isn’t sure what time it is when she wakes up. But Doctor McCoy is there,
checking her vitals. “Mornin’,” he says gruffly. “How are you feeling?”
“Sore,” Polina says finally. She’s never been beaten up but she feels like
she’s been kicked between the legs repeatedly.
“I’ll need to do a physical examination,” he says as he pulls a pair of gloves
on.
“Examination?” Polina has had enough embarrassment in the last day to last her
a lifetime.
“Relax,” he says. “I’ve seen it all between Jim and med school.” He reaches for
her but pauses. “I think you can do that on your own.”
“Thank you,” she snaps as she slides the panties down and off. The bleeding has
stopped. Sort of. But Polina feels like she needs a shower and a good
scrubbing.
Polina has had a gynecological exam before, from Nurse Chapel. She’d been
chipper and chatty and distracted Polina from the fact that she was naked from
the waist down while Nurse Chapel took swabs and samples.  
But here? With her feet in stirrups? And Doctor McCoy “hmm”-ing and muttering
between her spread legs? Oh, Polina feels like she’s about to die of
mortification. Her toes curl in surprise as he parts her folds to examine her.
A moan tries to bubble out of her throat when he swipes his thumb over her
clit. She’s so sore that she’s sensitive. Or maybe she’s so sensitive that
she’s sore. He swipes his thumb once, twice, three times more before Polina
finally groans.
“Do you want me to stop?” he asks. “Polina?”
She shakes her head, curls catching on the cot. “Doctor…”
She hears him chuckle as he presses his thumb against her. “That’s a girl,” he
murmurs. “Look at you, all red and wet.” Polina makes a high noise. “Come on,
baby girl. Let me hear you. All slick and ready. I could pull my cock out and
fuck you right now. Oh Polina. You’d be so tight, wouldn’t you?” His thumb rubs
her clit in tight circles.
Images flash through Polina’s mind. She wants him to lean down and lick her
clean. She wants him to fuck her—to get them both bloody— “Fuck!” Polina pants
as she comes. The orgasm burns through her like fire and McCoy rubs her through
it.
She’s still coming back down when he takes her legs out of the stirrups. His
hands waver slightly as he pulls his gloves off and disposes of them. “One of
the girls brought you some clean pajamas this morning when she heard you were
here,” he says stiffly, gesturing to a pile of clothes on the chair in the
corner. “And you’ve got the next two days off.”
“Thank you, Doctor,” she says as she slides her panties back on. “For
everything.” His cheeks flush a pleasant pink at her words before saying
“anytime” on his way out of the room.
 
Three months pass before she goes to McCoy again and even then it’s for
something unrelated. A landing party incident had her sliding off a pile of
rocks and scraping her hands up badly. She and McCoy make small talk as he
fixes her up. She’s about ready to go when he clears his throat.
“Are you bleeding anywhere else, ensign?” She flushes. He smirks at her. “I’ll
be by after my shift.”
Polina paces in her quarters. She’s already showered and shaved and even tried
to tame her hair. She put lipstick on, wiped it off, and reapplied it before
wiping it off again. She’s changed into a nightshirt but it makes her look
younger than she really is. She’s about to change when she hears McCoy at her
door.
He bursts in quickly and she’s about to ask if he changed his mind before he
says “I shouldn’t let anyone see me in the 17 year old ensign’s quarters after
hours.” Then his mouth is on hers and Polina is more focused on the stale
coffee taste of him than her own nerves. He murmurs filthy things in her ear as
one hand cups her small ass, pushing her into him. She can feel how hard he is
and she thinks I did that.
Polina ends up on her bed with her nightshirt pushed up to her stomach. McCoy
heads into her bathroom and comes back with a towel. “I plan on making a mess,”
he promises as he slides the towel under her hips. He lies down on her bed and
places one of her long legs over his shoulder before he presses kisses to her
sharp hipbones, fingers playing with the elastic of her panties.
“Doctor, I didn’t…” she starts as he starts kissing her through her panties.
There’s already a red spot blooming on the pale cotton.
“Good girl,” he breathes against the cotton. With a firm tug, the panties are
around her knees and then cast off on the floor by her bed. He holds her hips
to the bed as he flicks his tongue against her. Her immediate reaction is to
try to buck but his grip tightens. He makes obscene noises as he sucks at her,
tastes her—tastes allof her. He laps at her core and Polina glances down to see
the red smeared all over his nose, mouth, and chin.
His eyes are cloudy when he glances up at her and she can see how he’s
thrusting shallowly against her bed. She wants to offer some relief but he’s
back at her core with his thumb rubbing against her clit and all she can think
of is to chase her release.
When she comes, it’s with a deep groan of satisfaction. McCoy keeps licking at
her until she feebly kicks at him. He wipes his face on the towel under her
before heading into the bathroom. She can hear him washing his mouth out with
her mouthwash. She looks down between her thighs to see the red staining the
towel. Something inside her heats up. I could do this every month she thinks as
McCoy comes back out of the bathroom. 
End Notes
     the title was almost "written in blood" and I dedicate this to my
     ever-lovely Nina
     this isn't my first foray into menstrual kink and if you can find it
     on the depths of LiveJournal, you win a cookie
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