Sounds to me that firing the private neuro was a good thing. Even though they don't see MG that often, it doesn't mean they should not be able to recognize it when a patient walks in with it, or has symptoms which point to a possible diagnosis.
Hopefully the person you are seeing now can help you, or at least help you towards a diagnosis and treatment. If he/she gives you Mestinon, you should hopefully see some positive effects.
Good luck!