Good luck! I would be interested to hear if it works for you.
That's interesting that you have used it in the past to help with the migraines. I know many people use B2 (and multi-B) as preventatives, but I've never heard of using straight B12. Were you B12 deficient?
What did the FM doc put you on for your high BP. Some beta blockers, eg propranolol (inderol), are first line treatments for migraine. You may very well find this knocks out two birds (high BP and migraine) with one stone.