You know I think you may be onto something with the POTS/dysautonomia. I have that as well and it can be VERY debilitating, AND mestinon is the treatment for it, so you would feel better with mestinon! Your breathing symptoms and chest pain actually do sound a lot like my dysautonomia symptoms...and I have it as part of small fiber neuropathy, which causes me a lot of loss of feeling in my fingers, and feet as well. It makes me off balance. It's very hard to walk up stairs without being out of breath and getting bad chest pain if I haven't taken mestinon, but it's the dysautonomia causing that part, not the MG. The symptoms are different. I'd make an appt for a tilt table test and autonomic workup. POTS can be very, very incapacitating.