What Causes Stiffness And Severe Pain In The Neck?

hi i am 30 yrs old female working in a MNC with night shift having stiff neck and severe pain from last 2-3 years. The pain keeps coming and going after several intervals and some times gets so bad that im unable to sleep. Please advise if this can be a sympton of cervical spondylisis ? If yes than what is the treatment and medicine and from where i can get it?