Hi Dreamer, welcome to this site!
I would like to add something to Lizzie's post: recently I had to be admitted to ER because I couldn't breathe due severe swallowing and respiratory problems from my MG and from a bronchitis. They put me on oxygen (10 liters/min to start down to 0 when they released me from the pneumology dpt after a week). I discovered that some weaknesses from my MG rapidely almost completely disappeared during the hospital stay and reappeared after coming home. I guess it was all due to that complementary oxygen...
Maybe you should be checked for sleep apnea?
I'm also in a relapse period and I have PLEX every ten days which keep me afloat. Here in France, PLEX and IVIGs are used only for patients in crisis or as a support treatment waiting for steroids or immunosuppressants (Immuran for ex) to kick in.
I hope you will see some improvement in the near future.
Maurice.