http://en.wikipedia.org/wiki/Fasciculation

Sorry, when I read about "twitches" or fasciculations, I always think about ALS. (Sadly, I've known some people who had this horrible disorder.)

I don't want to scare you. It MOST likely IS the Mestinon. Check out the link. But, "sometimes" docs get MG and ALS confused. There have been cases where people with MG were misdiagnosed with ALS and visa versa.

HOW were you diagnosed?

Your Mestinon dose seems really high for a newbie. It really is MOST likely the Mestinon, I think.