I'm a 16 year old female. I'm not in the best shape, so lately I've been trying to exercise and eat healthy. I know cardio is how to lose weight and running tones you up, so I tried running on my treadmill. Shortly into my jog (about 3 minutes) I started to get severe chest pains, a bunring sensation almost. I walked for a minute or so, then started to jog again, but 30 seconds into jogging again, the pain was back and worse to the point where I had to stop, sit down, and catch my breath for about 5 minutes. Is this something serious?