How do i go from 138lbs to 115lbs as soon as possible?

i'm 14 and i'm about 5'3 and im in soccer, all of the girls on the team (high school varsity) take off their shirts and have rockin' abs(haha). Well, i'm about 135-138lbs and i would like to be 115-120. Does anyone have any suggestions or ideas for what i can do?