You need to talk to your parents about dieting. Your body isn't fully developed yet and you need to be very careful about any type of extreme plans. Yoyo dieting now, will make it harder for you to keep maintain a healthy weight when you get older.
You should also ask your parents to have your doctor run some simple blood tests to rule out medical issues that can affect your metabolism, such as hypothyroidism.
With when you posted this, it's not at all impossible. But it is a lot of weight for two months. The fastest ways to lose weight are definitely not always the healthiest, and chances are if it comes off fast, it'll come back just as quick as you lpst it if you don't stick with the way you did lose it in the first place. What I would do is a diet called Atkins. Its an extreme carb restricted diet. Basically, no carbs at all. That's the fastest way to lose weight, but usually used for event dieting. Like zneeding to lose 20 pounds before the "big day", whatever it may be. Google it, read up on it, and see if its for you. When I did it, I went from 172 to 148 in 6 weeks. But as soon as I quit the weight came back.