I do not think you can be undiagnosed Myasthenia after positive test. You can go into remission. but from your symptoms, you are not in remisission even if the antibodies are not currently positive. Yes, going off the immuno suppressants probably kicked off the MG again. Try this site: http://www.myasthenia.org/Livingwith...Materials.aspx. There is great info to keep on hand. I keep the list of MG bad meds, MG crisis protocool, and The emergency responder info with me always as well as a personal fact sheet of insurance, doctor names and numbers, list of meds and conditions, description of my MG condition and how I want to be treated in emergency: Support respiration, use Bipap and setting before vent and IV steroids. Keep several copies of the paperwork, the ER took all my papers and did not give them back.
Breathing issues are scary. I hope this helps

kathie