Oh my aching head

Hello, my migraines began back in the late 80's, early 90's.  At the time I was diagnosed, I noticed that the pattern seemed to go along with my menstrual cycle.  I would, and still do, get the flashing, jagged rainbows in my eyes, partially blinding me, prior to the actual pain beginning.  Thankfully, most of my headaches were never disablingly painful, but they are becoming increasingly so as I age.  I'm now 53, and even though I'm no longer menstrual, I still get the headaches.  I have used Midrin from the beginning, and have had doctors try to talk me out of using it, and have had me try other medications, but none of them worked on me.  They went back and forth with the generic thing, and now, I'm told none of the generics exist anymore.  What has happened to cause this, does anyone know?  I'd be interested to be informed on this front.