We've struggled with gastric reflux in our house for many years. Both our younger kids have it & both had major abdominal surgery to correct it. My son seems to be mostly good now, but my daughter has a dreadful time and is thinking about having the surgery again, although I'm not keen for her to go through that.
We started buying A2 milk about 9 years ago and cannot believe the difference it has made. I am a very cynical person when it comes to dietary fads, but this really helps our kids. We tended not to really notice until they drank ordinary milk again.
I'd suggest giving it a try.