Alright everyone, I am in need of some help. I am 5'7 and weigh about 125, Im not fat and I know Im not, but my belly is-- I want to tighten the muscles on it. When I stand up I look fine, but when I sit down its sticks like 4 inches over my pants and its sooo gross! I want to get rid of it for once, what are some good workouts I can do for it?
Fast results would be nice, but Im more looking for effectivness. I dont want to have to 24/7 suck it in anymore.

By the way I eat healthy- boneless, skinless chicken breasts and veggies and most of my meals. Special K for breakfast and a Special K bar for a snack, or an apple. Im only 18 and I dont want to always be so self concious of my belly and I dont want to be so jelous of other girls.. :-( help please?