Weird Sex Question

Ok so me and my man were BD and I was in a position that we usually do, but tonight it felt weird in my stomach.... almost like he was pushing my uterus up or something lol hard to explain. It wasn't that he was too deep it just felt like he was moving something 😳😳😳
Has anyone else felt this? I'm about 3 days til AF. Could it just be that my uterus is "full" ?? I've never felt that before.