What everyone said, it's probably just a matter of heightened perception.
I doubt you can just will your brain into changing your body, however the brain is pretty poorly understood so.. who knows? Maybe it is possible in some instances.
That said, I know I've been more conscious about my own body since I started questioning my gender, so it might be that. I know I've gotten flatter and more broad shouldered, but I'm sure that's only because I've lost weight and have been working on my upper body for a while. I've been recently told by a person I've met for the first time that I deepen my voice, and since then I've come to notice that I do unconsciously (or I've always thought my voice was higher), but I'm pretty sure I've heard the same comment a year ago.
Something I'm finding interesting, probably just coincidental, is that I seem to be sweating a lot more when I work out now. It always felt like it was just the males that were dripping all over the floor but these days I seem to be sweating all over the floor too. It's probably nothing more than me working out harder/noticing this for the first time. I know I'm probably trying very hard to find any indication of maleness in me these days that I'm bound to catch onto things I've never given second thought to before.
You might just be overanalyzing things like I tend to do these days. Or, you may have coincidentally happened to develop a thyroid problem? It would be awesome if we could just ask our bodies to produce more T, or less estrogen at the least..