I have been living with a daily headache for about the last 15 years. My neurologist has tried every scan and every new therapy out there and nothing worked. She finally asked for an MRI to examine the blood vessels in my head.
There was an incidental finding of three small unruptured aneurysms. If an aneurysm happens to press on a nerve, this could cause headaches. Perhaps you could have this investigated. All the best to you.