Medical weight loss programs are the way to go and I've tried MANY programs. I now am on a program thru my physical therapist's office. The program involves changing my eating choices and, of course, exercise. The junk food is gone. It's been replaced with whole graims, fruits, veggies and protein. I have lost 25 lbs in two months and have SO much energy. It took me 17 years to gain the weight so it will take me YEARS to get rid of it (if a weight loss program is drastic, the odds are it won't last over the long haul).
Find a doctor or trained professional who is an "expert" in the field of nutrician and weight loss. My specializes in teen obesity; he is working toward his PH.D in the field. I wish you were in the Gainesville, FL area; I'd refer you to him.
Any program that uses the word "Diet" isn't going to work.It's all about changing bad habits and getting your brain wrapped around the idea that health is what is important (not looks!). Best of luck to you, sweetheart. You know you CAN do it if you want it badly enough.