--like some sort of dysautonomia from where I'm sitting, possibly secondary to autoimmunity of some sort:

http://neuromuscular.wustl.edu/autonomic.html

You've given us some idea of testing you've had, but I think more specialized testing is in order, along the lines of the link above, or along the lines of the Liza Jane spreadsheets for neurologic symptoms:

www.lizajane.org