Mestinon makes me feel horrible why yet keeps me out of crisis...

My fiance is 26 yrs old and was diagnosed with MG when he was 5 yrs old. As a child his lungs collapsed twice before they knew what he had. He has had numerous plasmapheresis, steroids, immuniglobin therapy all to which he responded quite well, and spent much of his childhood in the hospital fighting for his life. He was in remission with no treatments for the past 12 years up until feburary when he had a bad tooth infection that sent him into crisis. Thats when they started him on mestinon and he felt horrible taking it from the beginning. He went into crisis again in april from a severe upper respitory infection and they upped the dose of mestinon from 1 60mg tab daily to 4 tabs. He cant not take that many. His stomach hurts so bad and his muscles twitch horrible, and he feels restless when he takes it. About weeks ago the pain in his stomach got so severe I had to take him to the hospital. They CT scanned his stomach and said that his lymph nodes are severly inflammed and to watch it. Well a few weeks later and the pain is much worse and I am sure it has somethnig to do with the mestinon as he never had stomach pain before he took it. But, what and why would the lymph nodes in his belly be swollen? What could be causing this pain and the bloating?