Tall Girl, I sent you a personal message with lots of info instead of putting it here. I also sent you my e-mail address so feel free to use that too! You can do this and wanting to is the very first and best step!
Just remember the very first thing that body image and self image are not the same thing. Your body image is exactly that, what your body looks like. Self image is who you are, your personality and such. Do not mix up the two thinking how your body looks somehow is a reflection on your personality and whatever. You are a beautiful young woman no matter what your size. You have wonderful qualitities if you think about it, good friend, compassionate, friendly, helpful, whatever you think is good about you so don't think being overweight is because you have a flawed personality. It has nothing to do with it. They are totally separate. This is probably one of the first things people have to get through their heads.
Let me know how I can help. I am always here for you!