I have hydrocephalus... I've had it since birth. It's an endocrine disorder caused by stress, like working double shifts for nearly a year with no sleep (put me in the hospital for a week in 2003) or being born seven weeks premature like I was. One of the major symptoms are massive, migraine-like headaches. What's actually happening is the spine produces too much fluid which fills the open spaces (ventricles) in the brain causing swelling and pushing the brain against the skull. If you've had a bad cavity or root canal, you know what a raw nerve touching bone feels like.
If your regular doctor can't find out what's happening, I would highly recommend seeing a neurologist or neurosurgeon, or at least getting a CAT scan. Adult-onset hydrocephalus is not rare and it happens from time to time. A man in my neighborhood developed it after an injury during a car accident.
Or it could just be migraines.