Constant Pain

So I've had my IUD for 8 months and I've had constant cramping since day one. It even hurts to have sex sometimes. I suck at taking the pill.  We hate condoms. My husband and I don't want to have kids yet but I can't handle this pain anymore. My periods are still coming, and sometimes twice a month. Went to get it checked and it is in its normal place, got an ultrasound to see if there was anything wrong up there but nothing. The doctors can't tell what is wrong with me. I have always had painful periods and nothing I've tried helps. I currently miss 3 days of school and work a month during my period. Anyone have any suggestions or help!?!?