Why is round 2 so horrible!!!!

La

Ok me and boyfriend are TTC so you know what that means (GOTTA GET IT IN AS MUCH AS YOU CAN:) )so anyway round 1 can be so enjoying and passionate for the both of us but when it's round 2 it's awlful like for example doggystyle becomes painful it's like my vaginal opening is being torn from the bottom and it gets so uncomfortable and i go into a distress

P.s. i went to a doctor he saids i have no STD or STI but i did have a yeast infection and a bladder infection.

But has anyone ever had similar experiences(if so wat u do?) or can give me any advice????