Please help......what could cause a headache like this?

I have pain only on one side. The pain radiates all the way down to the same side on my neck. It also hurts above my eye on that side and my eye is drooping. The temple area also. I would describe it as dull and deep......and when I walk around, it hurts even more. Can anyone please tell me what this might be or what I can do? I have taken 500mg of tylenol with a decongestant.......nothing helps. Only thing that helps is a heating pad