Why do I suddenly get headaches all day every other day?

I am generally a headache-free person, except when it’s that time of the month. And even then I only get a headache usually the day before my period. Lately, for about the past 2 weeks or so, I have been getting excruciating headaches, right behind my eyes, about every other day on average. Normally when I take Advil, my headache goes away within an hour. But since this started happening, Advil does absolutely nothing. I’ll take 4 like I normally do, and it won’t do anything. So an hour or two later I’ll take 4 more, still won’t do anything… The pain is so bad that it had me in tears a couple of times. I was hoping it would be something that would just pass but now I am getting very worried. I know I should see a doctor and I am going to make an appointment, but in the meantime I would appreciate any input as to why you think I might be getting these headaches. What is causing them? Is there something wrong with me? For the record, there have not been any lifestyle changes in the past 2 weeks that would trigger the headaches. Everything has been the same. But this is really starting to scare me…and take a toll on my well being! Help!?