Well, it's good that his temperature is normal, as I believe IMPA usually presents with a mild fever, and certainly did with my boy. If it did happen to be IMPA, Aston would likely need a much higher dose of prednisone than he is on at the moment (an immune-suppressing dose). My boy had been on a dose of 20mg per day + gabapentin and tramadol via our GP vet, but this did nothing to touch the pain, and when we were referred to a specialist his dose was upped to 100mg per day initially, so I wouldn't rule out something autoimmune just because he's already on steroids. Hope you get some answers soon, as I know how very frustrating it must be to see your boy suffering and not know what the problem is.