Hi I'm 12 and I have a big chest and people at school call me boob stuffer and older guys think I'm 20 or older but short.. I really don't like getting called these things I want smaller boobs but I just don't know what to do?.

Oh honey, I know what you feel. I had large breasts when was younger too. (still do)
Believe me when I say, they laugh now, but in a few more years, they will be DYING to get to know you. Ignore them. They are immature and very possibly jealous of you. The girls probably have to stuff, where you get it natural :)

There is nothing you can do. Your body will grow and balance out. You should talk to your mother and make sure you are properly fitted for a bra. This can help You may also want to adjust how you dress, wear more looser tops.

But the only way to reduce the size of your breasts is through surgery. And no doctor will do such surgery on a 12 yr old. When you are fully grown and an adult, if your breast are still too large for you then you can consider breast reduction surgery.