Have them check for auto-immune markers. What you are describing is exactly the symptoms I had for Hennoch Schonlein Purpura. Spelling aside, its unpleasant, but can be treated effectively. The immune system eats holes in your blood vessels, causing lack of blood flow to muscles, joints, organs. This in turn is very painful. A course of cortico-steroids can fix it up.
Anastas Dimitar Martin