Twitchiness can also be caused by too high of a dose of mestinon. If it is wearing off before the next dose, you need to move the dose, not take more. If it isn't strong enough, then that's different.

I am seropositive for MG. I have had too much mestinon and the typical indicator is lots of twitching, esp the eyes and face. But I do still have other twitches, with the larger muscles, like down my side. Those are for no good reason, other than MG. :-) Hope that helps.