Could Not Eat Veggie

Do you ever have the same experience like what I have now? I have a hard time to give my son vegetables. If I ask the doctor for advice, they always say that I should make some combination and mix of vegetables recipes. I did try all. But when the vegetable come inside my son's mouth and touch his tongue, he will vomit. I become hopeless. I don't know what to try anymore. I tried many kind of vegetables and I tried many kind of recipes. But it did not work. The only possibility is by putting those vegetables inside the homemade meat balls that I make my self. So he will never notice what is inside the vegetable. But then, I have to cook the vegetable first before I can mix it inside the meat. Does any one have a clue for me?