Hi I was smoking the other night and I started to get a sharp pain seemingly from my left lung. Thi was two days ago but now the pain seems to be coming from the muscles in my back which started to spasm when I massaged it. I have no pain when I breathe but left lung feels congested and seems to be producing mucus. Now I'm just hoping I do have lung cancer. I am 35 and smoked for 15 years.