Why can’t I breathe after running?

Patient: I’m 22 years old, 5 feet tall, and I weigh 105 pounds. I’m not overweight. And I’m a server, so I have an active job. However, whenever I try to go for a run (and not even a fast paced run), after 2 minutes, there is a huge pain in my chest, my head is throbbing, it’s hard to breathe, and I feel like I’m going to faint. What could be causing this? I don’t smoke, and I don’t eat bad food. I don’t understand why I can’t exercise.