Severe cramping 2 weeks before period is due

Just wanting to get an experienced opinion on this. I am having severe cramps 1 week and a half before my period is due. They've never been this bad before. I am not trying to conceive, but not actively avoiding it. However, my bf lives out of state and we have only had sex twice and the day after the second time, I got my period. So I know that I am not pregnant. Is there anyone who has seen a doctor for something similar to this and gotten a different diagnosis other than just painful periods? Ive been checked for endometriosis, fibroids, cysts, PID, HPV, all negative. And I refuse to commit to birth control as a solution to this. Anybody have any suggestions as to what this might be?