What Causes Persistent Headache Ranging From Severe To Mild?

I ve had a headache for over a month now that ranges from severe to mild but never goes away. It tends to get worse if I eat anything-no matter what even organic lettuce. When severe it s felt in my face and neck and I feel dizzy and weak. I don t take pain meds as they don t help. What can I do to stop my head from hurting?