Has your son ever had "tubes" in his ears?
Is he prone to ear infections?
Does he have balance related problems?
Does he have any phobias?
Does he have mild to severe dyslexia?
If any of the above are yes, get a copy of Harold Levinson's book "Phobia Free." You can find it for less than 2 bucks on Amazon under the "used" offerings with that title. In fact, from what you've described, I'd get the book anyway even if the answers to my questions were all no, if I were you.