What could this be, headache for a week?

This is not really something you should mess with, a doctor is the best person to see. However, if you really can't afford one, then there are blood pressure medications (natural ones) that can be bought in health food stores or vitamin outlets. They help control blood pressure. If your headache is worse when your blood pressure is up, then I would try this route. However, if it doesn't help soon, you really should seek professional help.