Another reason for heartburn and Acid reflux that is not discussed very often is maintaining a good posture. Here is an extract from an article I found:
" That’s right, the postures you adopt while you ingest food and directly after you eat are important, because they can either make food digestion an easy or difficult process for your body. For instance, sitting in a hunched forward position while you eat, and lying down directly after a meal, places additional stress on the stomach and can promote indigestion or heartburn.
Furthermore, wearing anything tight around your waist (belts, tight pants, corset, etc.) while you’re eating, places pressure on your stomach. Taut clothing constricts your tummy from expanding and moving freely, which is a natural process during eating and digestion.
When you put excess pressure on your stomach, it takes longer for your stomach to digest food. The longer it takes for your stomach to digest food, the higher your chances of developing indigestion and/or acid reflux. Therefore, improving posture during and after meals may help or prevent symptoms of heartburn."
Source: http://naturally-stop-acid-reflux.com/blog/2006/12/28/how-your-posture-is-affecting-your-acid-reflux/