Welcome to the forum, lukmuse!
There are many things this could be, including what I suffer with, Seborrhoic Dermatitis. If you rub in one place hard enough, does it become painful and raw?
I found that anti-dandruff shampoos made me worse, when I wash with them, I can feel my scalp stinging and burning. If this is the case, please stop using them immediately! Try Simple shampoo (with as few additives as possible) and speak to your doctor about seeing a dermatologist.