Headache and heavy feeling in head.

I seem to have a very mild headache. Almost ignorable. But it is constant. When I comb the hairs, there is a weird feeling and I apparently have pimples on the scalp. I feel slight heaviness in the back part of my head. I have a few questions regarding the same. 1-What could be the cause of the headache. 2- what all signs to look for. . Since it feels weird when I rub my hand on the scalp. And it feels like something is there. Even though, nothing visibly is there... What all to do to figure out. 1- If any, which test to opt for. 2-If any, which doctor to consult for? . Also there is a fear of it being one of the many brain related ailment, and somehow cancer comes to mind. I want to know how to make sure it is none of the that.