Hey, can you help me? (:?

Hi. I'm 12 years old, 5'3/5'4 and I'm 140 pounds. :O I have a chubby lil' tummy and I'm on summer break right now. And I haven't been doing anything but eating junk food and fascinating about becoming skinny. ): I have chunky fingers, chunky toes, chunky cheeks, and chunky thies. I have a small , and barley developing chest. I really want to lose weight so bad. I lost weight last summer but it didn't really change anything. :P I don't have any problem with exercising, besides know what to do and if it's helping? The only problem I'm really having is the diet problem. I'd be soooo thankful if anyone can help (: No stupid comments, forreals.