Hi Rach,
I experienced a sudden exacerbation of my MG symptoms when my prednisone was increased to 60 mg daily. The significant weakness that I felt lasted for about a week to 10 days, then gradually diminished to symptoms that were much more manageable (and a lot less scary).

Your symptoms sound severe. Don't hesitate to go into the ER, particularly with breathing difficulties. My current neuro said that she wouldn't start patients on high doses of steroids at home, specifically b/c of the risk of an MG exacerbation.

I hope your condition improves quickly.

Cate