Again, you should seek care from a regional referral university, meaning some place in a big city that treats many folks with your son's problem.
We have been to many ENT doctors and all I get is "we just don't know". I want someone who will actually listen to what I have to say and consider that I may actually know what I am saying. I am not a doctor but you can't diagnose my child effectively if you will not listen to the person that is with him everyday and consider what i have to say.
Try your nearest university ENT department...