It could mean u have Pneumonia
This "mucus" is produced when the inner surfaces of the alveoli become irritated from a non-self substance. The mucus can become quite thick and life-threatening. It can be clear or cloudy and be produced in the absence of infection. Observe it closely to see if there is any yellowish or greenish color (which would indicate infection). There are medications available (both prescription and non-prescription) to thin the mucus and make it easier to cough up. They are called "expectorants". Talk to your doctor or pharmacist for recommendations. If you have an electric aerosolizer for albuterol sulfate, replacing the medications with saline and taking several "saline treatments" will help.