Unbearable period cramps.

I need help. I need to know why my period cramps are always so unbelievably unbearable. The flow is always VERY heavy and very often has blood clots. Ever since I was 10 I’ve had these kinds of cramps, and I’m sick of it. I’m on birth control for the cramps but that still doesn’t stop the cramps or the flow. I feel like I can’t even move around sometimes, and I’ve stayed home from school PLENTY of times. I just don’t know what to do. They hurt so bad. Any advice will do.