Hi ladies, I feel your pain... I have agonising periods, so bad I can be rolling on the bathroom floor in pain, throwing up and fainting... but they're not particularly heavy.
The only drugs that work for me are tranexamic acid and mefenamic acid, taken together. They're excellent if I anticipate the pain, take them before it really sets in and throughout the period.
I consulted a naturopath (who said she became a naturopath because she had agonising periods) and results were good: prescribed magnesium supplements (magnesium EAP complex from Biocare, take 3 at night throughout the month with a bit of carbohydrate to aid absorbtion, and extra on your P when you're in pain). Makes sense as magnesium relaxes muscles, Epsom salt bath also helps.
Also vitamin E from ovulation for the second 2 weeks of your cycle (Solgar are good) (again take extra on your P with the magnesium if you're in pain) and Omega 3 fish oil.
I've read evidence that the pain is caused by Prostaglandins, which are raised by Omega 6 fats and balanced by Omega 3.
Finally B complex throughout your cycle and Starflower oil for the second half. If I take all the vitamins and avoid sugar / simple carbs consistently for a few months, I can get through a cycle pretty well.
Hope that helps it would be great to hear back from anyone who tries it.