Based on your height and weight, as well as your speed, I believe that the best fit for you is at the wide receiver position. You have the ideal size for a high school wide receiver.
My best advice for you is to work hard and perform very well in practice every day. In addition, what you need to do this (and every) offseason is eat healthy, exercise by doing weight lifting, and either jogging or going for a long run every day. If you do these things, you will get faster, stronger, and into better shape, which will greatly improve your chances of becoming a successful, top notch wide receiver in football.