When I was younger I was adamant that I was really a boy. This is probably because I was only interested in things considered masculine and I identified with my father more than my mother. But, really, I've always been a tomboy. In fact, only in recent years have I really taken an interest in "girly" pursuits, such as wearing dresses and make up. But even so, I never do it that often.
I am comfortable with my sex, even if, at times, I am a bit masculine.