i think i had an undefinable grief since i was 3-4 years old. but at that time, i didn't understand why i couldn't play boy games with the boys. maybe i didn't really understand gender "properly", i even still have problems understanding why it should matter if someone is male or female. the gender borders don't look absolute to me at all, even though a body is usually very obviously one sex or the other.
at around 8-9 years old, i started wishing, occasionally, that i was a boy. at ten i hated puberty because of secondary sex characteristics. i never wanted any of them, neither male nor female. i remember thinking at 12 that i wished i had an androgynous body so i could pass as a boy when i wanted to. seems like the reason i wanted an androgynous body was more because that allows one to choose whether to wear breasts or a penis on any given day. displaying all secondary sex characteristics at once would only mark me for bullying...
i'm fairly sure i was under 14 when i watched a documentary about transsexualism on tv. it made me realize what was wrong with me, but at the same time i also pushed the thought aside. something about that whole idea of a full transition just didn't fit (not to mention my parents' often expressed displeasure at the "gay lifestyle").
i was over 22 before the feelings of wrongness became very strong again. but not as bad as feeling like everything is wrong, it's not like i hate being female. i just hate not being able to pass as a man when i want to.