Hey, so about two weeks ago I had a fever and then got hit with a cough and cold. Even some sputum was coming up. The fever's gone now and I'm feeling better, but the cough is still sticking around, though it's not as bad as last week. There's still some sputum, but not too much. But what's got me concerned is that when I cough, I hear like this bell sound coming from inside my lungs. Any ideas on what this could be or what I should do?