Take a deep breath and don't panic. Coughing up pasty white stuff is not a symptom I have seen from my husband, who has lung cancer. The best thing you can do is #1 Quit smoking, reduce your chances, and #2 go see your doctor.
Good luck, I hope it is nothing. Please let us know.
I have been having the same thing lately, I must tell you it scares me also. Mine is very thick and usually just a little bigger than than a pinhead, but it seems to happening more often. Do you have any chest pain to go along with it?