What Causes Pain On Back And Sides Of Head?

Hi, I am feeling pain in the back and both sides of my head for last 5 days.. It started like a small pain in the area which joins the neck and head. Later both sides of the head started paining.. In the morning it will be like pain on the back side and later by after noon I would feel severe pain sides. Even I am npot able to turn or move my head. Even at times when I am laughing also I am having the pian. Could you please help me know why this is happening? Thanks in advance