I have Lems, but it behaves very much like mg, and I went downhill a lot too. I was on plasmapheresis three times a week and my main issues were shortness of breath and swallowing. My swallowing got so bad that I had to have a feeding tube placed. Since I was going down, my doc decided to try me on a course of rituxan in December and I am happy to report that I am much better. The shortness of breath is gone, swallowing is not perfect but much, much better. I am able to stand and walk around much longer than before and piddle around the house as I like to do. I am not perfect, but I would say 75% improvement and I feel like, with some rehab I will get stronger yet.
I truly hope you can the right treatment so you can get back to doing what you enjoy.