Yeah, I wore men's clothing from about 15 or 16 on... pretty much as soon as I had the money to buy my own clothes. People mistook me for a guy quite a few times while I was younger, but once I hit about 22, I think I just looked too feminine for that to happen. It didn't matter how masculine my clothing and haircut were, people just saw me as a girl... I'm guessing as a butch lesbian.
A couple months after my 24th birthday, though, I decided I was done living a lie, and started asserting myself as a man. I wore a binder everywhere I went, even packed (though I've realized the folly of my ways now... a rubber penis does not a man make). I used men's restrooms exclusively, tried to talk as low as my natural range would allow, and came out to everyone I knew. Did I pass? Heck no. But I didn't care.
Despite that, though, after 8 months on testosterone and the intense masculinization that accompanied it, I still have plenty of oh s*** moments, when I'm sure someone's read me, or I feel like I'm not binding well enough, etc etc. With my baritone voice, there's no way anyone could mistake me for anything but a guy... but that's just what happens when you spend 24 years in the wrong body.
SD