Hi, Abby! I have seronegative MG as well; no antibodies. At one time, there were 2 (out of 3 they tested for at the time); I've never been tested for musk. I get that trunk weakness and have to be careful if I lean forward to adjust the miniblinds in the window, I get this back and forth tremor like my body can't balance itself and my head wobbles and feels like its going to tip me into the window. Like you, if it's down in my legs, it's a really bad spell. Mestinon did not agree with me, made me incredibly jittery and sort of jerky feeling. Prednisone is what I rely on to pull me out of bad slump, I don't take it constantly, just if I am crashing. I have had short and long remissions, usually several months every year, and it seems to cycle on its own up and down. There are always down cycles that I iknow the cause of -- a virus, overdoing, big time emotional upset, etc. But it does definitely cycle on its own and is, to me, one of the most challenging aspects of the disease. Do I suit up for my good days, or for my bad days? I recently had such a bad low that I had trouble getting oxygenated for the first time ever, quite scary. I had to make some significant changes in my life to make my life manageable when I am in a down, including letting my dogs go to other homes and sending my son to live with his dad, don't know if its permanent or not. Very hard, but you have to rest aggressively and do all you can to stop the downward spiral so you can enjoy the respites!