D.D.
Have you done an elimination diet?
Both my babies were sensitive to dairy in my diet. So, if I ate any dairy, they were completely miserable with gas. So try cutting dairy out of your diet - it takes 3 weeks for it all to clear out of your system, so don't expect immediate effects.
The other big 2, in addition to dairy, are nuts and soy. If you don't get relief by cutting out dairy, then cut out nuts, then soy, and see if it gets better.
The other possibility is that he has outgrown his current dose of reflux meds. If he's had a growth spurt lately, that could easily be true. Remember that in a 15 lb baby, gaining 1.5 pounds is an increase in 10% of his size, and may mean that his dose needs adjusted. Talk to your ped about this.