Can i lose 200 pounds in a year?

hola I'm Selena, i'm 16 ill be 17 in October, and next year is my Senior year. I'm 5"7 1/2 and i weigh 338 pounds. All my life i've had a weight problem, i always have been the bigger kid, and ive been going to the same school my whole life, i really want to change the way i look and feel about myself. I want to show everyone i can do this! i've tried, atkins, low calorie, weight watchers, jenny craig. none of it works for me. I NEED help. any suggestions?