Mucous Coming out of throat?

I have had a weird feeling in the back of my throat, as if I have to cough, but nothing comes out, and I am constantly trying to clear my throat, then yesterday I actually coughed up some yellow mucous, and today when I woke up, I coughed up a little more. I also feel like its a little harder to breath. My chest hurts a little bit, when I try to cough. No fever, or runny nose, just mucous, and a little self induced cough to get the stuff out of my throat, even though most of the time nothing comes. I have no allergies, and I usually get Bronchitis once or twice a year. I am a smoker, and I take Oxycodone (as prescribed) for my neck and back problems. Any ideas?