Need more info.... There are many reasons you can have mucous associated with a cough - most are not that serious - like viruses/colds or allergies - but a deep cough with thick , discolored phlegm/mucous - especially if:: - it hurts in your chest to cough or -if you are short of breath or have a fever - - or -if the cough is worsening and not resolving on its own in 7-10 days - then you should see your md asap!
Maybe... If your mucous is discolored or associated with other symptoms like fever, then see your doctor. If you are short of breath with it or it persists for longer than 10 days or so, see your doctor.
Maybe. Need more information. What other symptoms? How long? Does it look like pus? Do you smoke? Repeat the question with more info and can be answered more effectively.