I dont know if this helps but I am 29 years old and I had that clear stuff too. it was very hard to cough up but when I did, it was alot. then i started coughing until i vomited on a regular basis. I went o the doctor 2 weeks ago and was tested. I was positive for moderate emphysema. They said the clear stuff was a symptom. I suggest getting tested. good luck
I've been fighting the same symptoms for about 6 wks now , so please someone shed some light on how to get rid of this mess ..