I have the exact same problem! I am 21, female, and I have this nasty phlegm everyday, all day, but gross and brown in the morning. I have had this for 2 years and It has been really bad ever since I had "mono". I've had blood tests done and nothing... I'm going to do a food allergy test and candida test next. Maybe that has something to do with it. Hope you feel better, your not alone! "/