Heartburn feels like a burning pain in your chest, just behind your breastbone in the middle of your chest. The pain is usually worse after eating, at night, or when constriction of the abdomen occurs when you lie down or bend over. While occasional heartburn is not cause for alarm, if you are getting it frequently however it may be an indication of a more serious underlying condition. Normally when you swallow, your lower esophageal sphincter, which is a band of muscle around the bottom of your esophagus, relaxes to allow food and liquid to flow down into your stomach. Once the food or liquid is past the sphincter, it usually tightens up again. If the sphincter relaxes abnormally or weakens, stomach acid can flow back up into your esophagus and cause heartburn. The backing up of stomach acid is also known to cause bloating.