hi, I agree with the great advice you received from TyTysMom, but if the vet has already seen him, and you have done the slow transitions when changing food, and he hasn't swallowed anything, it could be he's allergic, sensitive or intolerant of some of the ingredients or the protein sources of the kibble you have tried. Many bullies are allergic to chicken and salmon, and are also sensitive to grains. My guys are allergic to chicken, salmon, beef and grains, we switched their food 4 times before we found one that they tolerated. We are currently feeding them Fromm's Lamb and Lentil grain free and are having good results on this food. It does take up to a month before you will see any benefits or results from a new food change, as it can take this long for the old food to leave their system.