Hi! I think I would watch him tonight..since he is eating ok..and not vomiting after each meal..I would trust the vet that he might just be stressed over all the changes. Their little systems are very sensitive and he might also be picking up on some of your anxiety..if tomorrow he seems to still be breathing heavily and any vomiting..take him in. By the way..he is adorable! Congrats to you..nothing like a puppy!