Chiropractic...Try it. I've been fixing any and all types of headaches for years. It's almost easy. If you work with your chin down (like on a laptop), you can't help but mess up your neck. Other things you can do to improve your cervical spine. Get in the habit of raising your chin and gently roll your head back and forth. Do this often throughout the day. Change your pillow.
It might simply be a structural problem in your neck. Doc Sutter