Your stomach is an organ between your esophagus and small intestine. It is where digestion of protein begins. The stomach has three tasks. It stores swallowed food. It mixes the food with stomach acids. Then it sends the mixture on to the small intestine.
Most people have a problem with their stomach at one time or another. Indigestion and heartburn are common problems. You can relieve some stomach problems with over-the-counter medicines and lifestyle changes, such as avoiding fatty foods or eating more slowly. Other problems like peptic ulcers or GERD require medical attention.
You should see a doctor if you have any of the following:
NIH: National Institute of Diabetes and Digestive and Kidney Diseases