Can mucus come up from lungs without noticing it and without actually coughing it up? i have trouble telling whether mucus is from nose or lung.

You're not alone.: It's often difficult to tell whether the mucus comes from post-nasal drip or from infection or irritation of the air passages or lungs. If this has lasted a while or if you have other symptoms like fever, shortness of breath, tightness in your chest or headache, you should see a doctor. Often the source can be determined by history & physical examination. Dr. Anne.