I was wondering about
celiac as well....a very good friend of mine has a son who was diagnosed with celiac at age 8, up until that age he had episodes of what they thought was IBS, but then he started vomiting frequently, finally was tested for celiac and was positive for that disease. He adheres very strictly to a gluten-free diet, is now 15 and doing wonderfully.
It must be agony for you to see your son go through this! It is so hard waiting for test results, but it does sound like your doctor is willing to run as many tests as it will take to get a definitive answer. Hang in there.....((hugs))