I can not think of a specific diagnosis that explains your symptoms, and improves with excercise. Your case is very complex, and I would recommend having a second opinion at a large academic hospital. They should be able to review your tests and determine if other tests need to be completed. Good luck.
Suggest you see a nutritionist. I was experiencing the symptoms you describe and it was food related. I used to be overcome with tiredness and when I fell asleep felt as though I was losing conciousness. It took time and writing food diaries to isolate the offending foods but I feel great now. It occasionally returns and I know I've eaten something I should have avoided. Worth a try.