Reflux/Spit Up

My son is 16 weeks and has been dealing with reflux issues from the first few weeks. We've have him on Zantac and that seems to help with the gagging/chocking issues we had but my lord this kid spits up a ton! And it doesn't seem to phase him one bit. I've tried what seems like everything.. lots of burps, smaller feedings, sitting up a lot after bottle... he is mainly all formula fed (just stopped breast feeding this week... he was only getting about 2 feeds of breast milk anyways). I'm already using enfamil gentle ease and he seems to eat it fine but should I be trying something different? Different meds maybe? Anyone else dealing with these issues?