For 5 days now, coughing up a thick yellow mucus only upon waking, rest of day, just a cough, on amox 4 days, so far no help. what could this be?

Bronchitis: Most common cause of coughing up mucus is bronchitis, which usually clears on its own over time. Sinusitis can sometimes cause this if the drainage occurs while sleeping. Mild forms of atypical pneumonia can also cause this.If not better in one week, talk with your doctor again. If short of breath, chest pain, or fever develop, see the doctor right away.