I don't think that MG is very easy to diagnose. I have had symptoms for a year an a half and had been to four doctors. My coworkers (and sometimes my girlfriend) have thought it was in my head. I stumbled into the diagnosis myself by searching the internet. A neurologist confirmed MG four days ago.
I don't think that doctors have an easy time diagnosing this unless you can lead them by the nose. The symptoms have been difficult for me to describe and they wax and wane. Weakness and fatigue are common to just about every illness. What clinched the diagnosis was my eye muscle weakness.
It is also very possible to have two different problems, as well.
Hang in there.