Entire body weakness, anyone else?

22F with myopericarditis diagnosed 4 weeks ago. Anyone else experience extreme body weakness? My legs feel so weak, like they could give way when I walk. My hands also feel super weak, I struggle to close a tight fist. I only started feeling like this when I changed from ibuprofen/meloxicam to prednisone. I also have been needing to take oxycodone for the pain. Could that be causing this? Is this normal for myopericarditis? I used to be relatively fit - 10k steps minimum a day, gym and running.