Hello I Have Been Smoking For The Past 2 Years,

Hello I have been smoking for the past 2 years, I am 31 years old and have asthma. To treat the asthma I take one puff at night of 500 seretide and also one pill of singulair. About two weeks ago I noticed if I smoked a lot in one day I can have small streaks of blood in clear/tarry mucus in the morning. When I then stopped for a couple of days that went away. What can it be?