There is no such thing as “being a gender in one’s head”. Men and women can feel any way they want in their head — there are no rules. If you feel like you must be a particular gender — so bad that you feel angst about it — then you have a compulsive disorder. If you simply feel “I should have been born as a [boy/girl]”, then you are like a-lot of people — you don’t “fit the norm” — and that’s just part of being human.