Thanks for writing in,
From your history and symptoms it seems you are suffering from acute cervical muscle spasm. A course of muscle relaxants with NSAID's along with interferential therapy (physiotherapic modality) will help to relieve your pain. Avoid using pillows. Hot pack at painful site might decrease pain temporarily. Avoiding doing any strenuous activities which hurts your neck or shoulder.
Discuss with your doctor. He will examine you clinically and might order for an Xray of your neck to see whether you have developed any spondylosis
of cervical spine
Once the pain settles down, you can start exercises to strengthen your neck muscles.
Get well soon,