If you have Polymyalgia Rheumatica, it usually responds very well to Prednisone. Were you ever prescribed corticosteroids to treat the inflammation?
PMR and its companion disorder Giant Cell Arteritis (GCA) can cause pain, extreme fatigue, malaise, and anemia. It's called the anemia of chronic inflammation and appropriate treatment with steroids resolves it. I had it with GCA and had no energy whatsoever.