I kind of was a late realizer as well as an early realizer; I realized in my early to mid-teens, then repressed everything and stayed that way for around fifteen years.
But yes, I had a hidden girl, and she popped out from time to time; secretly borrowing my sister's bath products, enviously glancing towards the women's department in clothing stores while never finding clothes that I really liked in the men's department, sometimes even allowing myself to be persuaded by friends to go to parties in drag, or admitting out of nowhere to being a woman, but then laughing it off as a joke.
I sometimes wonder if I had a mildly dissociated identity, not like multiple personalities, but more like repressing my female identity so extremely that I sort of splintered for a while. I had big holes in my memory, and only after I accepted my identity, I recovered many of these memories. It was as if the most important part of me had been hidden away, almost only surfacing when nobody looked (but people still suspected "something" was "off"), while I presented this shell to the world, which gave a false feeling of "safety", but in reality made me very miserable.
In a sense, accepting myself felt like being glued back together, and after I started on HRT, I feel that way even more, to the extent of having stopped attempting to get rid of my androgynous side; I do identify as female consistently, but I see no shame in challenging gender norms anymore. While I have lost some stereotypically masculine interests because they were a facade to divert attention from feminine traits, I have retained others. I'm at a point where, as long as I'm me and fully me, I don't really care what people think. People who now see me as "still somewhat male" for still watching science fiction (seriously, that's more of a nerd thing than a guy thing) or action (like Homeland or 24), are just as stupid and wrong as those who saw me as a "sissy" when I watched Love Boat and Chicago Hope in my teens. I'll keep on watching all the genres I like, and at least now I can admit to liking all of them.
I suspect that my therapist also suspects me of having been somewhat dissociated, since she has used phrases like "you seem to now be well integrated" when I told her about these periods (though without mentioning dissociation, since it could be leading, even though therapists are trained to avoid that it can still happen). Thankfully, it has not interfered with HRT, as I have HRT to thank for now finally feeling whole again. It's yet another example of symptoms originating in gender dysphoria, which is very common, but sadly some health professionals still by default insist on the opposite. Thankfully, the ones I go to don't.