I am 24, and I am only now able to admit to myself that I'm trans. I had a period when I was 20 that I thought a lot about it. It was to the point where I was doing research and exploring how I felt. Sadly though, I went to visit my dad over christmas, and due to a few comments he made one night I shut down completely. I decided that I would just have to learn how to live as I am. I never had body dysphoria to an extreme. I've never really liked how I look, I've never really enjoyed my body, but I didn't allow myself time to think about it. I just forced myself through games, books, comics and (sadly) fanfiction in order to escape when I felt at a loss with myself.
Now, that I have had to admit out loud who I am, I had to force myself to confide in someone here in person. I knew if I didn't, I would retreat back to where it was "safe". I haven't been happy per se, I am able to play content pretty well. I mean, I am happy with my life and with my partner, I love school, I love doing things with my friends, and I am pretty content. As long as I never focused too much on myself, everything was okay.
So yes. I realized it later in life. I guess the distress I went though as a child should have clued me in before hand, what with the whole being crushed to find out I wasn't born a boy. Because of my mother I ended up just internalizing it and the end result is that I am dealing with all of these feelings and emotions now as an adult, and at the worst possible time (it's my senior year, and I have some huge changes in life flying at me).