Hi Tania, you could try and get your doc to speak with Dr Chris O'Callaghan who specialises in OI and knows a bit about ME/CFS. He's spoken at several ME/CFS conferences here in Melbourne.
Address: 455 Upper Heidelberg Road, Heidelberg, VIC 3084, PH: 94592699
Just to add the correction re an earlier post, he does
NOT believe that exercise is for all. I've heard from a few ME/CFS patients that he's excellent, uses more than florinef etc.
"Our clinical pharmacologist, the amusing Dr Chris O’Callaghan spoke on Orthostatic Intolerance in isolation…ie; not specifically how it relates to CFS but what it is and why it happens and what can be done about it. As it is a major symptom for many CFS sufferers the talk was received with interest. Since we have already spoken in depth with Dr O’Callaghan there wasn’t much new here for us. He did however state categorically that exercise does NOT help all OI sufferers. (I think he said 50/50 but I can’t be sure)"
http://parentingcfs.wordpress.com/2012/05/05/mecfs-awareness-week-2012-seminar-melbourne/
On another point regarding a sodium channelopathy many patients including myself who have used the anti seizure drug lamictal have found it excellent for headaches if that channelopathy is part of the problem.