I have REALLY painful scalp, radiates around the back of my head.?

My scalp is very dry, and frequently notice body rash and itching. Sometimes it seems to cause a really bad headache, almost like a sinus headache. Tried dandruff shampoos, steroid cream and tables, and antihistamines, nothing seems to work. It just sound so weird when I am trying to explain this to my Dr. but it HURTS!