How can I make my breast natrually bigger?

Okay. Im a 38C and i'm only 12 years old. My boobs seem big but they aren't . They look big but I dont wear push up bras or anything just a regular bra and sometimes sports bras. My breast are bigger than most freshman (9th graders) and I know i shouldn't be complaining but i got measured at the mall to see what size bra i wouldnt be in and i got a 38C but my breast don't nesciarily fit in the cup? I really want to make my breast bigger. Ive tried excersizing and other stuff and it still doesnt work. I'm a 7th grader and i have the biggest boobs in the entier school but it doesnt seem that way. I know some of the options arent possible like; gaining wait but it makes my butt bigger. i cant get pregnant because im only 12. i cant use injections or boob surgery....please i need suggestions..