"Cum inside me!" you cry out, your voice echoing in the club bathroom. The man who's fucking you - a stranger you met on the dance floor - is all too happy to oblige. He thrusts in and out, in and out, faster and faster, reaching one hand around to rub your clit as you moan in pleasure. You both climax at the same time, his cock pulsing inside you as your pussy clenches around it, drawing his seed deeper into your fertile womb. After a moment he pulls out, tucks himself back into his pants, and walks out without another word. You shakily pull up your panties, pull down your skirt, and totter back out to the dance floor for another round. You drink and dance and fuck the night away; by the time you call a taxi, you're barely able to stand upright.
The next day you wake up with a nasty hangover and blurry memories of the night before. You might have had sex with someone - maybe multiple someones - but you're not sure. You reach a hand down to feel your pussy, which is still wet from your own arousal. However, when you pull your hand back up to inspect it, there's no sign of any cum. Maybe all those strangers who finished inside you were just a dream?
Unbeknownst to you, those strangers were very real - and your womb has taken in every single drop of their cum.
The next week, you do it all again. And the next week. And the week after that.
A month later, you realize your period is late. You've never been that regular, though, so it's probably not a big deal.
Two months later, you're starting to gain weight, but it seems to be only focused around your lower abdomen. You'll just try to cut down on carbs and work out a bit more.
Then, about four months later, your belly seems to grow into a very familiar curve almost overnight. You stare at your reflection in the mirror, rubbing your hands up and down your belly, almost unable to process what you're seeing.
You are, undeniably, pregnant. You have no way of knowing who the other parent is, and at this point you have no choice but to carry to term. You will be forced to watch your belly grow big and round and heavy, feel the baby kick and squirm inside you, knowing that the person who did this to you could be almost anyone.
For some reason, this sends a thrill of excitement through your whole body.