There has never, as in absolutely, positively, without a doubt, and without any room for debate, ever been a time when I thought of myself as anything other than female. The only uncertainty I ever faced was growing up thinking I may have been the only girl of my kind. I cannot express how lonely that was, not thinking that any other human being on the face of the Earth would ever be able to understand why I was so unhappy. And I can't express how desperate it made me, how envious I was of my cis-gendered female peers, how furious I was (and still am, from time to time).
And it is because of this certainty that I am so abrasive with anyone that would ever suggest that I am a "man in a skirt" or that I will never be able to change my status as a male (no quicker way to make an enemy out of me than this, and a raging one at that). I never HAD status as a male, and I will not accept any argument otherwise. I am, have been, and always will be a female. In this case Biology is of absolutely no consequence to me. Maleness and femaleness have little to do with genitalia, chromosomes, or hormone levels, if ANYTHING at all.
I recognize that not all the women here share the experience of always bearing such conviction toward being called a female, but this has been my experience. I'm a girl, and I won't be told otherwise. I would debate this point with the Creator Itself, and just as harshly (though much more respectfully).