Over the weekend my boyfriend and I had sex like 7 times in 24 hours, each time I got off, normally I don't, after each time I got a weird cramp on the lower portion of my butt cheek which I figured was just from me straddling him, he's a little chunky, but this morning doing it myself I got that weird cramp again. I've been with plenty of guys with and without orgasm and never had this problem with any or by myself until now. Is this normal?