Stomach pain and nausea as soon as you finish eating is usually due to chronic gastritis, gastric ulcer, cholecystitis, pancreatitis and other diseases. People with chronic gastritis should avoid eating irritating foods and should chew and swallow slowly in their diet. After ingesting irritating food or rough food, the food will cause friction with the stomach wall during the digestion process, thus leading to pain in the stomach. Some people experience stomach pain at intervals after eating, and this condition is directly related to gastric ulcers. Patients with gastric ulcer have excessive secretion of gastric acid due to the stimulation of food for some time after eating, which induces a painful sensation when the gastric acid comes in contact with the ulcer surface. Some people suffer from diseases such as cholecystitis and pancreatitis, and such patients should avoid eating foods containing too much fat and cholesterol. As such foods can lead to high secretion of bile and pancreatic juice, once the bile and pancreatic juice are not discharged properly, it can lead to infection and self-digestion of the organ, thus causing symptoms such as stomach pain, nausea and vomiting.