Hi I'm 17, I Just Have A Quick Question If

Hi I'm 17, I just have a quick question if you could answer for me I've been sexually active since I was 15 and since I started being active every few months I'll have an extremely painful cramp type feeling in my lower abdominal. It's been going on for almost two years on and off, my menstrual cycle has always been irregular and i don't know what to do about this pain it really concerns me I've been to the hospital multiple times and they just give me meds for the pain and send me home I can't keep putting up with this pain it hurts too bad please help me find answer.