What causes continuous stomach cramps, pain and diarrhea and vomiting, it's been three weeks?

Needs evaluation: Most commonly, some acute disorder such as viral or bacterial gastroenteritis causes this problem. However it should be resolved faster than 3 weeks. At 39 years old, it would be unlikely to be a cancer problem, however your should be evaluated by a gastroenterologist. Diarrhea usually involves the lower bowel and vomiting usually involves the upper GI tract. Need a gastroenterologist.