Just started running.. is this pathetic?

I'm 17, 5' 4", and about 130 pounds. I'm not trying to lose a ton of weight, but I'd like to tone up and maybe lose ten pounds or so. I just started jogging on the treadmill three days ago. I jog at 6 mph with an incline of 3 or 4. I started with half a mile and now I do a mile. But the problem is, I can only go like a third of a mile at the most before feeling like I'm going to collapse. I start gasping for air and I just can't go any more, so I have to stop and walk. Is that normal since I'm just starting out, or is it especially bad that I can only run that distance without stopping?