Hi Saddison,

I think you might want to look at what you're eating.
One pound equals 3500 calories. And, as athletic (and young!) as you are, you're probably metabolizing about 2500 calories per day. If you were to limit yourself to 1500 calories per day, your body would burn 1000 calories of fat to keep you going. In 3 1/2 days, you'd lose 1 pound. At that rate, you'd lose 2 pounds per week.
By the way, I believe BMI is evaluated differently for athletes.