100-101 degree fever on and off 3-4 years. chronic left sided flank pain. fatigue, joint and muscle pain. any help with diagnosis?

Reasoning: While during medical reasoning we are trying to unify all symptoms and findings under 1 diagnosis, sometimes there is more than 1 condition explaining all symptoms. Your symptoms are absolutely worth further exploring in trying to find 1 or more causes and autoimmune disorders, chronic infections and slow malignancies are among possibilities. Imaging and bloodworm are usually needed.