Your symptoms are a flag for Parkinson's.
Needless to say you need an evaluation by a swallow specialist, which you probably have had.
Often, physicians will presribe a drug challenge. They will provide script for Parkinson's and if the symptoms disappear you have a provisional diagnosis.
Calcium-channel blockers will sometimes provide relief.
If you have Parkinson's there has been only one succesful use of stem cells to stop the progression, in March of 2008, in China.
If you haven't already, you should go to an endocrinologist, he can draw blood and do a special panel for your thyroid gland, and also he can order a scan if necessary. Could also be you had a mild stroke, and thus a cardiologist would be the specialist who can explore how your circulation is doing. You can also push on your lymph glands in your neck, see if they hurt or if they're swollen. If so, then could be you have an infection going on from various sources, in which case an ear nose throat ENT doc could decide where it's coming from. There's a chance you have cancer, since one of the signs is trouble swallowing, so you should see an oncologist who can examine you and do some labs, all sorts of tests, to see if that's what's going on. I say all these things excluding neurological, since that has apparently already been ruled out.