I swear by those Thermacare heat pads. They last for 8 hours (sometimes longer) and so I'll wear it on the front for a little while, then switch it to my lower back for a couple of hours, etc. I think I'm singlehandedly keeping them in business at this point, I buy so many!
My doctor prescribed a drug called Relafen to me, which as I understand is a mild anti-inflammatory medication often given to arthritis sufferers. You can also use ibuprofen; I am sensitive to ibu. so she gave me a scrip. She gave me a really awesome explanation of how to take it and why, actually.
She said that the reason women feel bloated, crampy, constipated, etc while on their periods is that the abdominal tissue is inflamed (think: swollen) in order to expel the ... you know, period juice.
I can't think of the word right now.
Anyway, the inflammation starts a few days before your period, so by the time your period actually starts (and you start feeling the pain), you're already so inflamed that one dose of Midol or Advil isn't going to cut it.
So she has me take one Relafen each in the morning and at night, starting 3 days before I expect my period to start, all the way until 3 days after it's over. Basically, you're never taking enough medication to feel "weird", but you're taking just enough to keep the inflammation from ever bothering you.
It really does work. I was always one of those curled-up-in-fetal-position-sobbing chicks until I started using the relafen. The other really important thing to do is to drink about twice as much water as you normally would to avoid water retention/bloating.