I don't know what to do ! help?

Try mixing his kibble with some canned food, and feed him twice a day-some dogs that only eat once a day will get nauseous because they are so hungry and it makes them throw up bile. There are many canned foods out there (my dog is very picky as well) and Merrick is a good brand. They have real meat in gravy, and many different varieties--both of my dogs love it when I mix it in with their kibble.