Open Question: Why does my left chest hurt when I inhale?

When I exhale it doesn't hurt so bad, but when I inhale it hurts pretty bad. It's been like this for a couple months and it's getting worse. It is located in the middle area of my torso on the left side. It kind of feels like something is clogged. Sometimes it happens at random, but it happens most often when I am doing something active that requires a lot of breathing. I am 15, 5'6'', 130 lbs.