Have you taken anything for the cramps/back pain? Ibuprofen always works wonders for me. I've never found the drugs specifically targeted to PMS symptions to be helpful, but straight Ibuprofen always works (although sometimes I need a lot of it--I definitely push the boundaries of the recommended dosage).
I also get a lot of cravings but so far haven't found anything that helps (other than eating, of course...
) Mostly I just try to ignore them.