Mary, Have you asked your primary doctor to check for obvious causes of fatigue other than MG? Like anemia, vitamin B12 deficiency, sleep apnea, etc.?
MG can "put me to sleep" after I go out and run errands. If your MG is so bad that you are really tired - if MG is the cause - then you might need to talk to your neurologist.
How much sleep do you get a night? Do you take a short nap during the afternoon? Do you have a good diet, one that balances out your blood sugar throughout the day? You know, like eating every few hours to keep an even blood sugar level and not eating too many things like sugars that quickly bring blood sugar up and then drop it way down?
There are a lot of possibilities for sleepiness, including a low thyroid and low cortisol. I think seeing your primary doctor is a great idea to try to figure this out.
Annie