You sound like a typical kid who is utterly clueless in this area of expertise. Don't take this as an insult, because you actually remind me somewhat like myself when I was your age (maybe even a bit older), which makes me nostalgic.
The thing you have to know is, nobody has a "4 pack". Everybody has a 6-pack (technically 8-pack depending how you look at it). The problem is that people have fat covering their abs. The best way to show your abs is to burn body fat (do this via cardio). Also, 200 situps is unnecessary. I suggest going to bodybuilding.com and reading some articles on exercise and nutrional science.
Also I'd really suggest that your diet be as clean as possible. Avoid candies and chocolates and softdrinks as much as possible.