he's trying to trap you into a baby.
that's how men collect lifetime partners these days.
the baby bond is actually a lot stronger than a marriage bond. i don't care what vows people say. if you marry someone and it doesn't work out and you don't have kids, that is IT. if you have kids with someone you are stuck with them for the life of that child.
you shouldn't have his baby because you're not married. you shouldn't have his baby if you ever got married, you just plain shouldn't have his baby.
any man who is so flippant with his penis to threaten to create a lifetime bond with a random side chick is not worthy of any of your time.