Given the wide range of possibilities, your doctor has her work cut out for her. In my opinion, you should stop the Elavil and undergo further testing. Your physician might even choose to have you examined by a neurologist, a move that I would endorse. That something needs to be identified. Whenever I get white patches on my tonsils, I have bad breath.
Tonsils are lymph glands at the back of the throat.
They serve to filter microorganisms out of the air we breathe. At these times, you should be examined by a doctor and probably have a throat culture for strep bacteria. I am certain that antibiotic therapy would go a long way in making you more comfortable and improving your breath.