Is this normal? Im begining to get worried?

I use to have intercourse and it didn't hurt me but now sometimes when Im having intercourse i would get stomach pains during it. The pain is hard to describe all i know is that it hurts especially more with each thrust. It hurts so much i dont want to continue. Does anyone know what this could be. It only happens sometimes. By the way I dont have any diseases im clean I just checked and im not pregnant. Could this happen due to having an empty stomach during sex? Please help ...Thanks