I'd talk to his pediatrician and get her advice. I never switched my daughter unless given the ok to from her pediatrician. If you've already tried Similac, Enfamil, and Gerber it may be something else causing him to spit up. For my daughter it was acid relux and she was given medicine for it. Fixed the problem right away. I had her take it for about a month before slowly taking her off the medication and after that she was fine.