I suggest to you that you get your cat on a more normal feeding schedule. Read that package on the food you are feeding him and follow the directions accordingly. They do not need or require 4 or 5 feedings a day... His problem could simply be you are over feeding him, so he throws it up..

I am glad the checked out fine at the vets so my suggestion is follow a more proper feeding schedule and measured amounts each day with maybe a treat or two a day if he acts like he is hungry inbetween meals. I feed mine Science Diet and they get 1/4 cup (each cat) in the morning and 1/4 cup in the evening. I use a 1/4 cup measure to scoop out their food.