Does he get sick every time he eats, or only intermittently?
Just a couple more questions:
Is your kitty acting normally otherwise, or is he lethargic?
How long has this been going on?
Chronic vomiting can have a number of different possible underlying causes. Some of them, such as organ disease, aren't very likely due to your cat's young age. Hairballs are the most common cause of vomiting up undigested food. It isn't usually as frequent as your cat's problem, but it would be worth trying some hairball medication. Laxatone and Laxaire are both good products. Give your cat a 1" ribbon once daily for four days, and then twice weekly for prevention. Another cause of vomiting right after eating is simply that the cat eats too fast. Try feeding him greater number of smaller meals if possible. If you feed dry food I would recommend trying canned, as its better for cats in general.
Other possible causes include intestinal parasites, partial digestive tract blockage, infection and more. Here is a link to a page that lists them all:
If the two above ideas do not help after a few days, your kitty gets worse, or he develops additional symptoms then I strongly recommend taking him to a vet for a diagnosis.
If you have further questions let me know. If this answers your question please click accept. Thank you.