sex hurts (plz read details:’))

i’m 19f and have had quite a few sexual partners. i’ve never had any issues like this though until i started dating my current bf. missionary is painless but if we ever have sex in doggy or prone position, my vagina hurts for about 2 days after. it hurts to pee and to wipe after peeing for 2 days, then its fine again. we also can’t have sex in those positions again until it’s done hurting. we’ve already ruled out sti/stds. i think maybe it’s just his size (hes super thick), but then again i’m a bit puzzled because i asked him if any of his previous partners have had pain like me and he said no. and i’ve never experienced it with anyone else i’ve been with either. advice?