My son has been dealing with headaches, stomach cramps, night sweats. i have taken him off gluten and its helping. why are the celiac tests still neg?

How long has he been: Off gluten? He'd have to be eating wheat products for the tests to be positive. Re-challenge him to see if the symptoms return. If so, repeat the tests for celiac disease.. With night sweats, has he had a TB skin test ? Especially if he has fever, he needs an evaluation for infectious diseases & other medical conditions with that constellation of symptoms.