it could be another issue but my fibro gives me bad cramps because of heavy inflammation

Mine is the same. I have fibro but also suspected endometriosis. Something my pain specialist said is there are also estrogen receptors in our muscle fascia so when our estrogen goes up the pain can also increase. Also, I second the inflammation. When I am doing well with my endo specific anti-inflammatory diet I feel much better with my cycle too. So sorry you're suffering through this!

I also struggle with painful periods & endo!

Mine have been terrible ever since they started. I was recently told I have endometriosis and cysts. Could be worth getting checked out :)

I have agonizing menstrual cycles every month. I just recently found out that I have developed some ovarian cysts and also uterine polyps that I had removed and biopsied. Thank goodness they found it when they did because it was found to be atypical but still benign. The surgeon said if I waited a few more months it could have been much worse. I highly recommend just getting it checked out and ask your ob/gyn for a pelvic ultrasound to be on the safe side. Good luck!