I am loosing weight

I am 14yrs.old. I'm gonna start acting very soon. I weigh 142lbs. and i wear a size 8 jeans in womens. I wanna weigh 120-125. I only need to loose 17lbs. The only thing that bothers me is my thighs are too big, my waist isn't skinny for like swim suits, and my arms are kinda big... but its muscle and i wanna make everything smaller. Like not too small but good enough until i feel good about myself. People tell me i'm not fat, but its hard whenever most of all your friends are size 0-5 jeans and your in 8. I just wanna know a diet plan i could use and exercise plans i could use. I do exercise and i watch my calories. But i don't know if thats all i have to do. i over exercise myself i don't wanna end up doing something bad to mess my body up cause i'm at such a young age. I just want answers and i need to know by the end of the month cause i'm gonna start auditioning either this month or next month, i don't know yet. but all i want is to be 17lbs. less , and 3 sizes smaller, and i want my arms to be smaller but still kinda muscular.
PLEASE HELP!!!
Thank You