Sudden diarrhea, later in the day fever 38.5. feel dehydrated. i do have a mild headache now but think its the dehydration?

Diarrhea, fever: The combination of diarrhea and fever is characteristic of a viral intestinal tract infection which should resolve on its own after a few days. Rest up, drink plenty of room temperature water, eat soft bland foods without roughage, take acetomeniphen for fever. If not gradually improving, call your MD for advice and/or evaluation.