If I cough up mucus do I have the flu, the cold or bronchitis?

I was coughing up mucus today. What sickness do I have? I don't have a sore throat or anything so I don't think it's bronchitis but the only websites that reference coughing up mucus online are sites referencing brochitis.
If I cough up mucus do I have the flu, the cold or bronchitis?
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