You decide the best course of action is to go back to the source: the costume shop where you purchased the uniform in the first place. If nothing else, you can use the changing rooms there to turn yourself back into a boy.
You expect to be hurrying there with great haste, but you find yourself walking slowly and deliberately, almost pigeon-toed, with a regal gait befitting a girl of your age and appearance. This is no time to worry about manners, you think to yourself, but you're unable to change your pace. The things you've been doing out of fun--the talking and the posturing--you're now doing automatically as if you've brainwashed yourself.
To test what's happening to your mind, you think of your favorite color, green. "My favorite color is green," you say aloud in an angelic whisper. Then, you think of another color and say "My favorite color is violet." All thoughts about your favorite color suddenly grow murky, and just as suddenly reform. Now all you can think of is violet. You can't remember what your favorite color really is, just that it is definitely not violet.
"My favorite color is...blue," you whisper. Nothing seems to change this time. You still believe it's violet. Just then, you realize that you've never consciously referred to purple as violet before. That's yet another prim and proper thing creeping into your mind.
So you can change your boy memories into girl memories by stating them out loud, but once they're changed you can't change them again. Furthermore, if you say something that's already true about yourself, you still have the chance to change that later. Case in point, when you said your favorite color the first time, whatever it was, and then were able to change it by speaking a lie the second time. That's as clear an understanding of things as you can work out for now.
You put your analysis aside for the moment, as the costume shop comes into sight...