Heartburn or acid reflux happens when there is a back flow of acid from the stomach up into the esophagus. When the stomach muscle sphincter is loose, acid can flow back anytime, not just after a meal. Bending from the waist and wearing tight garments can cause heartburn too. Some people also have delayed gastric emptying and so food remains in the stomach long after a meal. People who have a peptic ulcer complain of stomach pain that is worse on an empty stomach. Ask your doctor to explain the signs and symptoms of your condition as well as the treatment of your problem.