Welcome back gal499,
Sorry to learn of your problems. While it seems you are headed towards MS, I would prioritize your health with regards to your thyroid and blood clot before you worry about the possibility of MS. You are quite lucky in that if it were not for the migraines, you might have dismissed everything until it all became dangerous to your health.
Take the opportunity you have been blessed with to get your major issues out of the way. Stick with the specialists for your probable MS, your blood clot, and your thyroid. You might find that some of your problems are directly related to your thyroid, but that is not a guarantee.
Take courage. You are doing the right things and I am lifting you up in prayer. In the meanwhile, I would encourage you to check the board on this site regarding your thyroid specifically because you might find answers therein.