6 year old with intermittent stomach pain for 1 month

Over the last month, my 6 year old son has had 3 incidents of upset stomach. Each time he complains of intense stomach pain, usually has a temp in the 99s, low appetite and lower energy. This lasts 24-48 hours. Once he had no GI symptoms, one time he had one incident of diarrhea, and one time he had one episode of vomiting. He will go from feeling fine to feeling sick all of a sudden. No prior history of stomach issues, no difficulty with bowel movements, no food allergies or noted connections to certain foods each time. In between issues, he is eating and behaving fine. What am I missing? I feel it is too coincidental that they are all unrelated as 3 separate incidents in a short period when there is no prior history of stomach issues. What could the possible causes be? Gallbladder attack, appendicitis, h pylori? Could any of these be possible?