I suffer from daily chronic headaches due to a rare syndrome called Mollaret's Meningitis. It is my thoughts after having this for 25+ years that many people are misdiagnosed in the hospitals. There is not one clear etiology for this. Mine comes from having the chicken pox as a child. Once you contract the virus, pieces live in you for the rest of your life. There are other symptoms that can help you identify the syndrome. These include stiff neck, back pain, nerve pain, photophobia, phonophobia, severe headaches and sometimes rashes. Also fibromyalgia. If you are having any of these symptoms you may get some answers at
http://mollaretsmeningitus.ning.com/. I am not a doctor. But if you are suffering from daily headaches and are not getting any answers, you may want to research a little bit further. Feel free to email me for more details. And if you have been diagnosed with this, I would love to hear from you.