What can I do to get skinny?

I need to lose at least 15-25 pounds by July 16th! I have to so that I can fit into my swimming suit when I go camping! I'm 13 years old and a girl. I wear extra large adult shirts and size 16 pants. I weigh about 160+ pounds. I'm 5 feet 2 inches tall. I at least need to be able to walk up a hill or the stairs without getting winded. I don't know why I'm overweight because I don't eat that much. I only eat fast food 2-3 times a week. I only have desserts 1-2 times a day. I do eat 3-4 meals a day. Sometimes five. I don't like running so I need a workout plan that doesn't involve running. Please help me! Thanks!