Actually, a little more than 3 weeks. Ever since I had the flu around New Year's, I have had this headache. My neck is also stiff. The headache is across my forehead. Pain relievers help it a little, but I've stopped taking NSAIDs yesterday, and the headache really hurts today. Kind of freaking me out, since I'm not one to usually get headaches. But it definitely started when I first got sick with the flu, so it has to be related, right?