Ask the vet for Zofran to help settle his tummy. It works better for us than Cerenia. You can also try slippery elm bark syrup to help soothe his tummy and GI tract. It will also help a little with nausea. Lastly, get simethicone, or baby gas drops (Mylicon) and give 0.3mg or 0.5mg every 8-12 hours. If his tummy is upset, he won't feel like eating. If he's not eating, the body can't get the nutrients it needs. You're feeding him a great food, but you might try plain meat baby food for now and then mix with his regular food once you get the nausea under control.