Hi T.,
I really feel for you. My husband went through this a couple of years ago and it was so hard to get a diagnosis. Have you ever heard of Meniere's Disease? Check it out on the web. That is what he was finally diagnosed with. There is medication (which initially makes you very lethargic), but it helps with the dizziness. He did have it for quite some time, but is fine now.
While they were trying to diagnose him, something else they tried was some kind of physical therapy. It had something to do with the fluid and crystals in his ears. I wish I could remember more info for you, but I just remember him going...so maybe that is something to look into too.
Good luck. I know from his experience how frustrating it is and how it afftects you mentally also. Please hang in there!
D.