What does it mean when your neck hurts to the point where you cant even put your head down on a pillow cause it hurts to do that,ive had headaches for months but nothing shows on tests,no fever,have hip implants,not sure i can sleep on stomach.so why?

At this time I recommend being seen by a neurologist to determine the type & cause of your headaches. Can they be caused by chronic osteoarthritic spurs in your neck vertebrae or are they muscle contraction tension type headaches? Simple xrays of the neck can demonstrate osteoarthritic spurs & narrowing of the foramina where nerves exit the neck& travel up to the scalp. ?An MRI of the neck&head