I get dizzy spells when I have like a thyroid flare up, and it is so good to finally have someone describl exactly how I feel, It is just like being drunk and the world spins. I have Hashimotos, and my immune system attacks my thyroid, I have found that my world will spin when this happens, When my dose gets adjusted I feel better, but It comes back, and that's when I know to go have it adjusted again, for me it usually means my dose is too low and needs to be upped. Have you had an auto antibody test for your thyroid?
Have you spoken to your physician? Your blood sugar or blood pressure could be low, one of those medications or any combination of those medications could cause dizziness. Take care and I would try to recall if there is a pattern to the dizzy spells and relate this to your physician. Good luck.