5"5 115 pounds? really fat!?!?

so I'm really fat teenager and need to lose weight. I already excise but now I want to stop eating...or eat very limited amounts. today all I had was ginger ale for breakfast, gronala bar for lunch and handful of grapes and lettuce for dinner. right now I'm drinking a coke to fill me up. how bad is this for my body? I don't really care how bad I just want to lose like 7 pounds