I have my phlegm for haw many weeks but i do not have cough and running nose. what is the problem on me?

I have also got this problem.I had it a few months ago and went to see my doctor who listened to my chest which sounded OK but he did give me a course of antibiotics.The problem still didnt clear after I had finished the course so he sent me for an xray which came back clear.He then suggested I take a cough syrup that can be bought in the chemists. After taking this it gradually went away.I now have the cough back again so I will try the cough syrup again. If the phlegm is white then it is not a chest infection. I do not smoke so I am not sure what causes it. Try taking a syrup that is for dring up the phlegm and hopefully it will clear up.