Pain after sex. help!?

Alright, so my boyfriend and I have been together for 8 months. When we first started having sex, it was great. Occasionally, we wouldn't use condoms because I'm on birth control and they've always hurt. But lastnight we tried having sex for the first time in a while. We used a fandom and tons of lube. It hurt extremely bad at first, but the pain lessened a bit. Then we started doing it doggie style, and he thrashed me. I woke up today sore down there, but we tried having sex again..only this time it hurt so bad that it almost didn't go in..well it still hurts and the lower part of it feels extra sore and kinda firm. Is this just because I'm tight? Or something else?