I believe I have chronic Lyme, and I've been having symptoms of MG...( mostly leg weakness and on and off tight muscles in upper back, some blurry vision but 66 years old as well. I did 9 weeks of reading and found Stephen Buhner an herbalist who's father and grandfather were both doctors to be extremely knowledgable about chronic Lyme. You can find him by searching Buhner and Healing Lyme.
His book healing lyme is very informative albeit you have to look alot up because it's written for lay people and professionals, however I think he really knows what he is talking about and his website is simple to navigate. There are groups on FB for his and other herbal methods.
If there is a chance you have MG some Antibiotics can make it worse. I don't want to do more Antibiotics either. He offers lists that can help you figure out what you might have . Please let me know if you still think you have MG and what your symptoms were. I'm being tested for it but awaiting results and would like to think it's Lyme and not MG