I am 25 years old female. Never been seriously ill. For last 10 days I feel pain on the back of my neck, on the right side. Pain goes up to the back of my head behind the ear and in front under my collar bone, precisely under the joint of collar and chest bone. I don't have any other symptoms of any disease. It just hurts when I try to rotate on my right side of when lying on chest. Using diclofenac and it helps. What could it be, could it be dangerous and how can I help to myself? Thanks so much.