I have had a headache for almost 3 years, it started April 9, 2008 and was originally diagnosed as an ocular migraine, I get the strobe light like flashes occasionally, however the pain has never gone away. I have had CT scans and nothing was found. The pain is in the front left side of my head going from my eye back to my ear, in that entire region of my head, and at times it is so severe, I cannot have anything at all touching my head. What can cause this?