I've had chronic headaches for as long as I can remember, I've seen tons of doctors, tried all sorts of medications and nothing's helped. Everyone has a different theory and none of them are correct.
A piece of information that all the doctors seem to brush off is that when I was 8 I hit my head hard on the corner of the wall. I didn't lose consciousness as far as I can remember and the only reason I can remember the injury is because the surface of my head where I hit it hurt for about three years. It hurt to comb or brush my hair because my scalp was so tender in that area. It eventually stopped hurting so much but I've had chronic headaches since then.
I've given up on doctors and they've given up on me, I've learned to be careful and control the headaches so I can do more things, but they never go away. I don't know if the head injury has anything to do with the headaches and why they would last for 7 years, but I thought it was worth asking.