Don't worry about it. You'll grow out of it. Ever since second grade, when my hair gets long, I cut it off and donate it ( 30 inches so far! Now where's that fist pump smiley?
). Every time after I cut it off, people think me a boy. I'm not a boy... Not in any way. I don't have that big of a waist, I'm well endowed, but I'm tall. Really tall. Was 5 foot 6 by seventh grade... Which was the height of boys... So yeah. It got a little awkward sometimes. Should have seen the stares I got when I wore a dress!
I'm not sure who started the whole 'stop worrying you'll grow up' thing though, I'm not too worried, what goes, goes; as long as it doesn't go as people thinking I'm a girl all the time.