Pains in the left side of the chest?!

Ever since I was about 6-7, I had been getting these pains in the left side of my chest. It would happen once in a while and then go away in the next five minutes. Nowadays, I've been getting pains on the chest at least once a day and it wouldn't go away for another 30-60 minutes.

It feels like a sting, I only get the sting when I move a certain way or breathe heavily. I was wondering if someone knows a way for it to go away. I can't tell if its a muscle or stress or something else.