What Causes Persistent Headaches?

I've been suffering headaches everyday for over a week now I'm tierd all the time and now my gum's are bleeding but dont hurt. I've not changed anything in my diet i just dont understand why? I'm 25 and healthy weigh 8 stone and I'm on the pill cerazette i get regular sleep and have recently been to the dentist and my teeth are healthy i hope someone can help.