What Causes Dull Intense Pain In The Base Of Skull?

I have been experiencing a constant dull, yet occasionally intense pain at the right side of the base of my skull for about a week. Sometimes pain radiates down the right side of my neck, others up the right side of my head to the crown of my skull, but is always present to some degree at the base of my skull. Pain is constant, dull, and grows worse with exertion. Any advice?