Am i overweight?

i am 13 /5 7' or 5 6' / 124 lbs./ i dont rly appear fat, but i have been called horrible names by the boys in my grade. (twinkie, fat, whale) idk. if i am overweight what could i do that would be affective, fast (like to loose weight before summer?) and not harmful to my health?? thx so much in advance! <3