Three days ago, I felt this pain for the first time - it is a mild to moderate (but mostly mild background ache) ache that is located on the back of my head in the lower left quadrant of my skull - but much closer to the ear side than the middle, and also toward the base of the skull. I could feel the pain in the bone just behind the ear. I don't think it is a sharp or shooting pain. I am not normally prone to headaches (except when extremely stressed), and even if I do get headaches they are always in front, never at this location. And this is the third consecutive day that I am feeling. I am concerned about the fact that it is sudden onset, persistent and such a specific, localized area. I am very prone to hypochondria and of course the first thing I am thinking of is brain tumor. I am an otherwise healthy female in my late twenties. Has anyone else experienced this? Any insight is appreciated.