Why does my daughter often complain about stomach pain?

Hi doctor,

I have a question regarding my daughter. She is 6 years old. Her symptoms are tummy ache around the abdomen area. The navel looks slightly swollen only during pain and she feels full after a few bites. The pain usually occurs in the morning upon waking up. In the last six months, she has complained about the pain at least once or twice in every few weeks. Recently, it has increased in occurrence and severity to about a few times a week. The pain severity varies from mild to too painful to walk and then it eases up. The pain duration may vary from about 30 minutes to over an hour, but not very much longer than that. Once the pain is gone, she is up out of bed and runs outside to play. What seems to have helped her most of the time is warm black tea. Her eating habits vary, and therefore, I cannot draw a connection to food. The only food taken on a daily basis is cornflakes, bread, fresh milk and bananas, which she has always had.