How to lose fifty pounds in four or five months?

I'm 13, 5'3, and 150lbs. I know I'm basically obese (though I gained the weight evenly all over my body so I don't look obese, just chubby) and really need to lose the weight before the next school year, since I currently home school and will be going to public school next year. I'm fine with exercising, but it's dieting that I have a horrible time with. Ever since I can remember, I've been ADDICTED to sugar. When I was a little kid, my parents would only let me eat a little bit everyday, so I didn't get fat. But eventually, since I got older, they stopped making me only eat a little bit, so I basically went crazy for about two years and gorged myself with candy bars until I puked. I'm not blaming my parents for this at all, they warned me I would get fat. So now I'm obese, and can't get rid of all the fat because I'm addicted to sugar. I don't want become anorexic or anything, but a lot of the time I feel like that's my only hope of getting skinny. Is there some way I can still eat some dessert and lose weight? Like maybe one small thing a day? Or do I just have to completely do away with sugar for good, which my parents have advised me to do, especially since diabetes runs in my family. And is there a way I can lose weight without my breasts shrinking? I'm a C cup right now and really don't want to shrink to an A cup or anything.