Size 12 is not fat at all, especially if you are tall!!!
Im a size 10, and its crazy because i think of myself as fat too but when i actually think about it, its not a 'skinny' body that i want. If you offered me a 'skinny' body, i'd give you it back. I really like being curvy, for me its toning. I would love to be more toned, maybe if you did a few toning exercises you'd feel better about your body, but you certainly dont need to lose weight and become a 10.