I am a 13yr old girl,am I overweight?

i am a 13yr old girl.i am 5ft 2inches nd i weigh 144 pounds nd i am 28inches round da waist.i have been soo unbeliveably self conscience bout my weight lately its gotten soo bad that i have avoided every single mirror in sight whenever im out with my friends i cnt stand to look at myself.jst want to no what wud be a healthy weight for a girlmy age nd height.i do 40-50 sit ups evyerday,i lift arm weights nd hve recently been using a stepper fer 10 mins a day buh nuin has worked!am i over weight?