Welcome to the Migraine/Headache forum. You have a kind of tricky problem. Changes in hormone levels are one of the most frequent triggers for migraines, but when this trigger happens can be before, during, or after your period. Basically, it is just one of those things you have to accept as a female.
I've never heard that Migraine with Aura(classic migraine) is any more dangerous than without(common migraine). They are pretty equal with standard symptoms, once you get past the aura stage.
The thing that actually concerns me the most is that you have been on birth control so long. No female should be on the pill(any variety) for more than 4 to 5 years, especially if you haven't had children yet. You should discuss this with your gynocologist as soon as possible. From what experience I've had with different OB/GYNs, they have all have recommended taking a break every so often, and let your body naturally for a while. Apparently, controlling your cycle artificially for a longer time can make it much more difficult to get pregnant, once you are ready to make that step. It also make you more susceptible for blood clots, which can kill you, or at least give you a stroke.
I would really suggest getting off the controlled hormones for a while (there are other methods of birth control if you need that). You will still be affected by your hormones, which will still probably trigger a migraine, but if you have an abortive migraine medication, that should take care of it whenever it occurs.
Best of luck and let us know how you are doing.