Hi there, if you think and concerned about it being an infection keep getting in touch with your doctor and asked to be checked properly sometimes with an chest infection they can hear it through a stethoscope crackling sounds wheezing e.t.c.In saying that when I went to see my consultants at hospital they said they could hear wheezing in my chest, I just said it is always like that, when I was asked to breath in and out what a noise I made, but second breath in and out I managed to make it sound better.I had blood tests done, sometimes they will do a chest scan also.I must say though when I had chest infection my phlegm turned green but I don't recall it tasting bad just more mucus and chest and back aching and tightness around the rib cage area.I am not a doctor, but if you are concerned keep in touch with your doctor or start feel really rough go to the E.R.I am just a member on this great copd site. A chest infection can make it hard to breathe in and out also.Go or ring your doctors again and tell them what you have said on your post here and see if they can give you anything to help.But please remember I am not a doctor I am only going by my own experiences with my own copd Emphysema.X