You say you have a small hiatal hernia (I’m assuming the size of 1cm was determined by endoscopy?) It’s possible it’s gotten worse since you were tested? Have you tried having it adjusted by a chiropractor or Naturopath? Have you tried the heel bounce exercises (when you wake up drink a full glass of warm water and bounce on your heels)? You can also try stretches such as hanging from a pullup bar (hang on to the bar with your hands and bend your knees so that your weight is pulling your torso straight. Since I’ve been doing these things I’m able to eat more before feeling full and I’ve had less belching.