If it hurts that much, have you ladies asked your doctors about the possibility of endometriosis or PCOS? I always had awfully painful periods, and often had pain in between my periods for no apparent reason at all. Nothing over-the-counter would do anything at all for the pain, and heating pads only helped a bit. Turns out that I had endometriosis and adenomyosis (which is endometriosis that grows in the muscle of the uterus). The nurse practitioner at my gyno's office said I had PCOS as well based on a hormone test, but through 2 surgeries and 2 ultrasounds, my ovaries have never been seen with cysts on them.
But at any rate, all of those conditions can cause heavy pain during periods. I had a supracervical hysterectomy this year because of it (meaning I still have my ovaries and cervix) and I feel a lot better, but I couldn't get any relief at all for yeeeeears. I had my hyster done by a specialist in Atlanta, and I have a couple of fliers that I picked up from his office if anyone is interested (I can scan them). Just some info about symptoms and adenomyosis in teenagers that I picked up because I was curious to see if I could've actually had this disease for the entire 14 years I was menstruating rather than assuming it had developed in the past 8 or so years after I turned 18.
In the meantime, heat always helped me more than anything else (heating pads and hot baths), and some people find that cold packs help too. I could never go the exercise route, because exercise always made it worse for me (probably because my uterus was full of lumps that shouldn't have been there)