I love to dance but my weight. ?!?!?!?

I'm 13 and a girl and i love to dance i do acrobatics. My dance studio is very into the whole acrobatics stuff (the owner trained with cirque du soleil) and she puts on this cl called production acro. I really wish i could be in it but to me the girls in the cl are either tall and muscular or short and skinny. I'm like right in the middle im muscular but im not tall. I think i weigh alot i weigh 119 pounds and i'm 5"3 i think that is fat for me at my age. Like paris hilton weighs like 90 pounds and shes in her 20's. Any ideas how i can lose at least 30 pounds until september (thats when the next season of dance starts) i don't eat that well.. and i do exercise!