Hi Manolis,
Thanks for the extra info...
Have you tried self traction? This is where you grab your head on the skull near the ears and just try to lift your skull off your spine by a millimeter or two. That may help ease some pain.
You don't mention which movements of your neck/head makes things worse...please tell more on these movements.
Also, it does sound like there is a 'pinched nerve' for want of a better term.
Good luck!