Nancy,
Keep working on your preventive regimen. Barometric pressure changes are one of my worst triggers too, but with mu current preventive regimen, I'm getting far fewer Migraines ever thought the weather has been so horrid for them this spring and summer.
Also, talk to your doctor about the possibility of something you can take when you know the pressure is going to change. I know a couple of Migraineurs who take Diamox when they know a weather front is moving in.
If your doctor can't help with this, it may well be time for a Migraine specialist. See our directory of patient recommended specialists if you need help finding one.
Teri