Painful/uncomfortable sex

I will be 36 weeks tomorrow and over the past few weeks sex has become increasingly uncomfortable and almost painful at times. It feels like he is hitting the back of me or like my cervix or something. We have tried many different positions and they all feel this way. Does anyone else feel this way?? What could he be hitting that's so uncomfortable? He says it feels different and like he is hitting something as well. He's not small but also not abnormally large or anything if that matters.