I am an extremely self-conscious person. I am 5'8 maybe 5'9 and weigh 128 pounds. Is that fat?

My mom always tells me that muscle outweighs fat. I do play a lot of sports and I guess I would consider myself a bit muscular. I am also trying to get myself a two pack...which I used to have until the holiday season rolled along. Any good exercise plans to get it? I've been doing 200 sit-ups a day and 100 push ups.