I have a hard grape siz lump on the back of my head right above the hair line, it hurts, especially when pressure is put on it, it gives me a headache?

Probable cyst: Based on your description, you probably have a cyst growing just below the skin, although it is hard to know for sure without actually removing it. It is a simple outpatient procedure to remove these, and if it is already grape sized, I would recommend removing it sooner rather than later (especially now that it is causing a headache!).