It's risky to start AAS on your own when you're taking a catabolic steroid like prednisone to do the exact opposite of what anabolic steroids do. The prednisone will affect the use of anabolics. So in my opinion, I'd work with your doctor and see if he can recommend an alternative treatment. Prednisone will kill you, by the way, if the disease doesn't get you first.
Having said that, if you chose to ignore my advice above, I would do a lot of research and if you feel like experimenting, you can (I have done the research) control your immune response through anabolics without risking your life on prednisone. The right combination of test/deca/stanzabol can suppress your immune system without slowly killing you.. But, I hesitiate to go any further in explaining because I really feel you need to stick with your doctor or find one that can treat your condition with AAS, not catabolics. You may want to try a TRT doctor and approach him.