I fixed it by drinking concentrated lemon juice (one lemon in one coup) thirty minutes before every food. There were not enough stomach juices for proper digestion, and stomach tries to push undigested food out after while. Lemon juice triggers stomache juice excretion and helps to start it. It has to be concerned, mild will just dilute juices.

I am prescribed hydrochloric acid supplements for the same reason. They've eliminated reflux for me and have helped my digestion.