sharp pain after sex?

So my boyfriend and I don't have sex at all since he's always tired from work and were always busy, but last night we did, and I woke up in the middle of the night with this sharp pain in my pelvic region almost as if it is really sore.. It wasn't rough sex either. I took some midol to maybe help with the pain and this morning it is still sore. What could've happened? Could it just be that I'm not use to it anymore?