that is actually way too thin for your age 11-12 yr olds should be that weight u need to eat more and remember if u dont feel like your weight is good excersise but believe me your not overweight it may seem like it but your not.
When I read this, I thought I was reading about myself. So anyway, don't worry! The people who are like 5' 7" and 140 lbs. are most likely to thicken out when they hit thirty. So don't worry, at your high school reunion, you will be good and thin, and they will wish they were you! You may also have a really high metabolism, I know I do :)