Don't know what this is

When me and my SO have sex sometimes I get a sharp like warm pain across my belly button area all the way to my butt like right down the middle don't really know how to explain it, it doesn't happen every time, I would say like 5 times out of 20.

No idea what this is. I was told by a doctor once I have a twisted pelvis I don't know if that has anything to do with it or not.