My diagnosis took 5 neurologist about 5 months to confirm. I think most people with MG have suffered through lots of tests and doubts from co-workers, bosses and families that they are either crazy or lazy.
The tensilon test I had in February 1997 confirmed I had MG. After having a thymectomy in April 1997, I was in remission for almost 11 years. When I started having problems again in 2008, the symptoms weren't exactly the same and it took 4-5 neurologist another 8 months of various tests including single figer EMG nerve conduction tests to finally diagnose (after another tensilon test), that I was simply ouf of remission for my MG. Since the symptoms are often not diagnosed from the most common tests performed (as stated above), I would recommend you try and convice your doctor do the Tensilon test. It's generally done in an ER or hospital setting because of potential life threatening reactions (heart).
Today, I'm taking mestinon with some improvement in my fatigure and left leg weakness. Good luck!