Secondly, it can be due to hiatus hernia (occurs when the upper part of your stomach protrudes into your chest cavity through a weakness in the hiatus (opening) in your diaphragm.)
Treatment is antacids and prilosec.Also eat smaller meals, especially at night. Don't lie down right after you eat. Use 2 or 3 pillows, or a foam wedge, or raise the head of your bed to prevent discomfort..
Thirdly it can be gall stones or pancreatitis.