Generally the change in your hormones causes migraines if you're susceptible. I have found that Depo Provera helps, though it is also know to cause migraines.
Same here- I take birth control, without the inactive week...therefore I have no monthly cycle (sorry guys, I know you love to hear these kinds of things!)
My doctors say that is perfectly fine- you can go up to four months without a cycle, therefore four months without a migraine enduced by hormones...
Now if I could just get the rest under control, like the weather and the other triggers like stress and foods etc!