I am very sorry to hear that your return to work attempt did not go well. It sounds like you need some more time for rest. A month is really early to return if you're been having the issues you've described. Taking those two months on disability to rest and focus on recovery is just what you need to do.

Have you tried cognitive rehabilitation therapy? I have worked with several nurses (all type A personalities I might add...) who had a difficult time returning to work. Fatigue was one of their greatest barriers to success. Two of them really felt a difference when trying a stimulant such as Ritalin or Concerta. Might be work discussing with your physiatrist...
Jena