What to do if i have had a headache for five straight days, what could it be?

5 day headache: If this is a new onset headache for you, then formal evaluation with a physician is important to be certain this is nothing worrisome. There are many benign causes of prolonged headaches - problems with teeth, sinuses, neck, sleep issues - or infections of certain types - but there can be other more worrisome issues that should be evaluated.