When I breathe, I feel as if I can't take a big breath - or even yawn correctly! It's scary, I've also been coughing up mucus for about three months ever since I had developed pneumonia, but that is over now, but the mucus is still here. I'm afraid that mucus or fluid could be building up in my lungs and making it harder to breathe. Strangely, I only noticed the breathing problem about a week ago. I don't know what could be wrong besides a possible future lung collapse or a mucus/fluid buildup