Help on cause of chest pain?

Yesterday I was moving a futon, that I've moved hundreds of times, and when I reached across my body to pull it with one arm something on the left side of my chest area popped. Right after I couldn't put any pressure on my shoulders or chest area at all. I have asthma and it became increasingly difficult to breathe as well. I just brushed it off, expecting it would be better the next day. However, here I am and it hurts worse today than it did yesterday. I am fine if I don't move and take shallow breaths, but I would like to have a better idea of the cause of this pain and if I should see a doctor.