I am sorry that you are feeling so poorly.
I remember that one time I took Prednisone and got off of it. I felt like crap in every regard and it took some weeks before I felt myself again. I have no problems with arthritis, but after Pred my joints very aching like crazy, i was stiff, I cried all the time and had tantrums. It is really like a Prednisone hangover that takes some time to get over with. But I am truly sorry for all the health problems you have without the Pred. I personally refuse to take Pred ever again myself. First, it didn't do anything for me and second, it scared me how much mind-altering it is. And having a moonface still three months after being off Pred does prove to me that this drug is powerful in mean ways.
Exercise is a good idea, just as much as you can handle and something that you like. Have you tried very gentle yoga? It is fun and simple and very beneficial for warming up the muscles and joints and get moving. I enjoy taking very long walks with my dogs (sometimes brisk, sometimes just strolling) if I don't feel up to anything else, because I am too achy or too tired or too weak. If you don't have a dog, you should get one :) - provided you have the space, the time, the money and the permission from the landlord if you rent your home. Dogs make you happy, they are something to care for, they depend on you and make you feel good about yourself. I have a chihuahua (well, he is 95 % chihuahua and the rest is mini pinscher) and a Pembroke Welsh Corgi puppy. I feel miserable without my dogs, but I am getting OT here. Maybe your neighbor has a smallish dog that you can borrow for walks? Sorry for getting carried away :).
So your doc took you off all your meds? Do I remember correctly that you took 6MP?
I wish I could help you, but I don't know quite what to say other than i hope you feel better soon.