I’m so sorry you are having to go thru this ordeal…it is truly terrible. I had Covid pneumonia in November 2020, and have experienced cramping muscles that eventually resulted in progressively weaker muscles over my entire body and severe all over bone pain. Tried everything, meds, daily soaks in Epsom salt baths, creams, lotions etc., Chiropractic adjustments and massages (which did help) are expensive when you need them at least weekly! My PCP suggested Physical Therapy and it has helped so much. Gently stretching along with light weights and my favorite the underwater treadmill. The warm water provides buoyancy which protects the joints along with the walking, stretches the muscles. This has helped me so much, I was doubtful in the beginning but so thankful I went!
Hopefully after all possible medical causes are ruled out, you can try any or all three (Massage, Chiropractic, Physical Therapy) of the treatments that have helped me. Hang in there and never stop trying to find help and get better. The long Covid after effects are new territory for us all including doctors but the good ones are trying to find the answers that so many people need. Take care!