Why is my stomach so fat? What am I doing wrong?

I'm not overweight. I'm a 19 year old male, 6'1" and I weigh 140 pounds. I jog for 30 minutes 4 or 5 days a week and lift weights 3 days a week and eat healthy but my stomach is just blubber. People tell me I'm too skinny but they just see my arms and legs and not my fat stomach. I just want to get rid of the fat and see a 6-pack is there anything else I can do?