Tummy ache during breastfeeding may be caused by improper diet, or gastroenteritis, appendicitis and other diseases. 1. Improper diet: If you don’t pay attention to your diet during breastfeeding and consume too much spicy and stimulating food, it will stimulate the mucous membrane of the gastrointestinal tract, which will lead to stomach pain. 2. Gastroenteritis: Gastroenteritis is an inflammation of the gastrointestinal mucosa caused by various reasons, the causes of which include pathogenic microbial infections, reflux of digestive juices, food, etc., which manifests itself as epigastric pain, diarrhea, abdominal distension, and so on. If you suffer from gastroenteritis during breastfeeding, you will experience stomach pain. 3. Appendicitis: appendicitis is caused by blockage of the appendix lumen or bacterial infection, and the typical symptom is pain in the right lower abdomen. If you suffer from appendicitis while breastfeeding, it can also cause stomach pain. There are more causes of stomach pain during breastfeeding, and it is recommended to consult a doctor for a clear diagnosis when this symptom occurs.