What Causes Neck Stiffness And Pain At Back Of Head?

i have been experienceing pain in various places from the bottom of my shoulder blades and upwards. Pain comes and goes and moves about however the most persistent and painful occurs at the back of my head in the soft part on the right hand side - just above my neck. Sometimes i feel as if i can no longer bear to hold the weight of my head. Generally my neck stiffens and i can not rotate it to the side (the right side). Lying down does not make the pain go away but it does give sligh relief to the rest of my body which seems to tense up when i experience the pain. I am a 30 year old female, around 9.5 stone.