Massive butt cramp

Ok so this has happened two times now. I will get this horrendous butt cramp pain for about 20 minutes. it is so bad I can’t even sit down, I literally scream out in pain it hurts so bad. I almost called 911. I don’t know what it is. at first it was all along the bottom of my pelvis, then just became a cramp in my rectum area (sorry tmi). im so scared it’s gonna happen again. it’s not like a stomach ache. it’s like a muscle cramp feeling. the first time it happened was after I had sex. I was high so I wasn’t really aware of the pain but I knew something was wrong. the second time I was sober and I literally saw stars. it’s better now but i still do feel a little pain when i press down. idk what it could be?? ill get it checked out by a professional, just wanted to see if there was anyone on here who can offer some advice. thanks!!