My stomach is KILLING ME

Okay. So I've recently started sleeping with someone new (we were good friends back in highschool, reconnected about a year ago and now we are sleeping together and dating and now we are officially an item effective last week)

He's great in bed. He's got an amazing personality. And he's stepped up to be there for me and my daughter. Even before we were dating and sleeping together he'd just spontaneously buy her a box of diapers or an outfit just because.

Anyways. We both have a high sex drive. I'm not super flexible LOL. But after we sleep together, my stomach cramps up like crazy. It's like I have a huge painful gas bubble inside and it makes me cry. It's that bad. We were waiting to sleep together till we were official. So basically for the past two weeks after we have sex, I pee, we clean up and whatever. And an hour later my stomach cramps. It hurts to stand sit lie down everything. My vagina doesn't hurt at all. It's the inside all around. We're both clean. It normally takes a full day for the pain to subside. What do you think it is??