chronic headache in back of head

I experience severe headaches approximately 3x/month.  I have had an MRI of my brain, but the doctors have been unable to tell me what causes them.  I have been diagnosed with migraine headaches, but I do  not have the typical symptoms (i.e. spots of light and dizziness).  They are always center the back of my head and the only relief I get is with a perscription pain medication and lying down.  If I sit in an upright position, my head throbs horribly and the pain is, at times, to much to bare.  I can have a really good month,  but then I seem to pay for it the next month.  I have tried migraine medications, but they do not provide any relief.  I'm not stressed or depressed about anything. Usually, the day after a bad headache, I feel very spacey and my eye focus is kind of hazey.  The headaches started approximately 5 years ago at age 25.  I was in several car accidents  just prior to the start of my headaches.  Could the  headaches be related to a missed injury to my neck?  Could something more serious be going on that I should be concerned about?  Any insight would be greatly appreciated.

[Fellowsufferer]

I also have experienced similar headaches and been very frustrated by attempts to get help from the medical profession.  A wide variety of doctors and medicines have been tried with little to no benefit.  One odd thing that seems to help at times is to filter the air, either with a high quality mask or high quality air filters.  If I use the mask and get better, take it off and get worse, I assume it is something in the air that I am reacting to.  I also use a CPAP machine which has a HEPA filter and it also helps.  I have had these headaches from my late teens until now and I am 57.    

[neyners]

My headaches are in the back of my head and start when I lay or lean back on the  back of my head. Even with a pillow I will get a trobbing, and painfull enough to cry headache. Usually last the rest of the day.

[gtcar]

i broke a windshield with my head back in 78 and i still have the neck/headaches. some of the headaches are migraines or cluster type, some are due to my cervical joints having spurs and degenerative discs. this is due to the accident. my chiropractor says my neck is at least 20 years older than i am. i've found that when meds aren't enough try an ice pack or one of those gel things you freeze wrapped in a towel, and sit with it sometimes i go for over an hour but it works wonderfully. i sometimes have to get up during the night out of sleep and take a couple pills and ice it down. when i go back to bed i take the pack with me and lay on it till i fall back to sleep. this works for me.
then, some of my headaches are weather related. either an approaching front or a change in barometric pressure will trigger one before it even gets here. take something at the first little sign and knock it out asap.