Ive had a headache for 3 days. first day came out of no where & was beyond horrible that meds didnt help. its now lingering off & on & pain is mostly back of head & sides but also moves around. also had food pois 4 days ago. what could this be?

Bad headache likely related to food issue. Could also be many other things. CVOID-19 test negative?. Did you get you flu shot? If so, not likely flu. Anyone else sick in family or at work? What is going around where you live. Ask a health care provider. Could be Berry aneurysm but rare. Meningitis if going around there?

Are you certain that the diarrhea was caused by food poisoning & not by a viral infection? Headaches can be part of a viral infection or from dehydration caused by the diarrhea. Migraine can follow a bout of diarrhea, also. If headaches persist see your MD or a neurologist for evaluation & testing. In the meantime take tylenol or, if your stomach isn't upset, advil as needed.