Am I overweight?

I'm 14 years old, about 5'9" and I weigh between 130-140 pounds depending on the day. I know according to this I'm normal, but I have this bulge in my tummy area and I'm extremely weak when it comes to athletics. For example, I can only do about 10 pushups, 40 situps and barely a pullup. I know it's pathetic, but what should I do?