Black specs in mucus...?

Our family recently got sick (flu, I think). Fever, chills, congestion, coughing, vomiting, diarrhea, sore throat. It's been miserable and going on for over a week now. Today I was in the shower. I coughed up some phlegm and spit it in the shower. I looked at it and noticed it had black specks in it. I thought it might be food particles at first but it was not. What is going on with me? This illness is horrible. I'm not a smoker, btw.