How old is he? Are you only hand feeding or do you have a feeding cup? Some chams don't like to eat with an audience. Is he pooping? If there is poop then he is eating somewhere. I would try a less stressful method like cup feeding before you start feeding him when he is gaping. Gaping means he is stressed and angry, not really the mood for a relaxing dinner... If he continues to refuse food when you cup feed then he may be bored, try mixing it up with different feeders. No one feeder should be more than a fourth of his diet.