Exercises that build chest muscle?

I'm looking for a way to get a nice, strong chest. I'm turning 13 this month, 5'6" and weigh 124 pounds. I have a lot of muscle (biceps, abs and chest). However, I wish to get very strong pecs and abs. I need some exercises to build muscle. I run everyday on the treadmill and eat healthy. No junkfood at all except maybe one cup of chips every 2 weeks. So what should I do to build chest muscle? All i have is two 5 pound weights and my arms to help for pushups. And what do I do for abs? thankss