my son got bad breath before, together with swollen tummy, bad appetite and white tongue. at that time, i didn't know that these were the symptoms of over-eating (later i knew it from a chinese medical article), and i still forced him to eat and drink milk. after a few days, he stopped drinking milk at all. i regret so much that i neglected these signs.
if your son got these symptoms, just let him eat one or two meals fewer. my son recovers now and starts drinking milk again.