Stomach discomfort when lying down may be caused by stomach diseases such as gastric ulcer, over-eating and epigastric occupations. 1. Stomach diseases, when suffering from chronic gastritis, reflux gastritis, gastric ulcer, gastric retention, gastric cancer and other diseases, it will lead to an increase in the tension of the stomach when lying down, resulting in symptoms of stomach discomfort, and change position, the stomach can not immediately adapt to this kind of performance. 2. Eating too much, if you eat a lot of food before lying down, due to the extrusion of food will lead to stomach discomfort. 3. Occupation in the upper abdomen, when there is pancreatic cancer, liver cancer and other occupying lesions, when lying down, due to the pulling of local tissues, it will lead to stomach discomfort. For serious cases, timely medical treatment is recommended.