Also, there's just not always a "neat" diagnosis for every disorder. I have "new daily persistent headache", meaning that I started having a bad headache many years ago and it never stopped. I've had extensive testing over more than six years and nothing has shown up but we're confident in this diagnosis--my neurologists, psychologists, psychiatrists, GP, etc. Personally, I know that i can't definitively rule out the notion that there is a psychosomatic aspect to this, meaning a mental causes as opposed to physical trauma. But even if there is it doesn't make the disorder any less real or painful. I've been seeing mental heath professionals since I started getting these headaches and things have only gotten worse.
Psychosomatic or not, your problems are real and they're very difficult--don't let anyone tell you differently. As januk said, fibro is a possibility, though I'd expect hat you'd be complaining of more severe full body pain and potentially experiencing bipolar -like symptoms. Regardless, keep trying to find something that will help you--I guarantee that you'll eventually find it. In six and a half years I haven't found anything that gets rid of my headaches but I have a pretty good idea of how to make them as tolerable as I can.
One more quick idea. There are additional tests you may want to consider. For example, though you've gotten MRIs, MRA/MRV tests reveal potential blood vessel problems. A lumbar puncture may be in order depending on your symptoms (this has a lot to do with associated secondary symptoms such as aura)--your neurologist should be able to determine whether it's worth looking into. Also, sleep is often a problem for those of us with headache problems. A polysomnogram, or sleep study, could reveal some potential problems. Also, try anything you can to take some control of your headaches--biofeedback training, types of exercise that you can tolerate, along with many other strategies.
DX: NDPH, Recovered CRPS
RX: Lamictal, Concerta (Methylphenidate), Clonazepam, Wellbutrin XL, Namenda, Oxycontin, Oxycodone, Melatonin, Magnesium supplements.
PRN: Ketamine nasal spray, Celebrex, Migranal, Haloperidol, Zyprexa, Lodine, Zofran, Phenergan, Thorazine, DHE IM, Droperidol IM, Toradol, Reglan, Ambien CR, Provigil, and all triptans