How to get my cat to stop barfing?

Ever since we've gotten this kitten he barfs A LOT its almost like a woman's period (seriously, a whole full week of barf barf barf barf barf every month) now he is about 6 years old and it has continued going on, and we've taken him to a vet. The vet says there is nothing wrong with him and that he probably has a hairball and he's trying to get rid of it and that it just so happens he ate so the food came up while trying to get rid of the hairball, but I don't think that's the case at all. Yes, he sheds a lot and licks himself a lot more often than most cats (espesially in the private area) so maybe that has something to do with it, but do you think there's anything we can do to get him to at least barf less? (we've tried lots of different kinds of cat foods that are for his digestive and such but it doesn't work)