Steroids like prednisone. can it help with severe chronic fatigue ?

It depends: Steroid is generic name. Prednisone is in that class o drug. It has anti-inflammatory action so it helps fatigue associated wit inflammation as seen in autoimmune diseases like lupus, rheumatoid arthritis. It can actually cause steroid myopathy and fatigue in some people. And long term use can cause many side effects. Not a treatment for cfs.

Not generally: Unless you are suffering from addison's disease i would not expect it to. You need to have appropriate lab work like acth and cortisol levels at a minimum which would help in diagnosing your condition. These drugs have severe consequences if used improperly. You need to see a physician.