Whenever i walk first or climb the staircase, i easily get tired and feeling shortness of breath and chest pain. what is happening to me?

See doctor: Do you have asthma? Anemia? ... So many differential diagnosis, you need see your doctor, period. Good luck.

See your doc: At 21 you should not have these symptoms unless you are very out of shape. If this is a new symptom you need to be evaluated. Tell this story to your doctor. You may need a stress test, you definately need to be examined.