My boyfriend has been having stomach aches and constipation for about a week now. Any remedies?

Headache, vomiting, diarrhea, stomach aches, and constipation were all present the first two days. Only stomach aches and constipation are present now. We have tried the brat diet (bananas, rice, applesauce, and dry toast) with no results and drinking more fluids fluids. Neither has helped very much.