I Had A Cough And A Sore Throat Last Week

I had a cough and a sore throat last week and I went to the doctor to see if I had strep and didn't. Then I was starting to get over it and now I have a really bad cough my throat is kind of sore. It's way worst than last time. Last night I had brown stuff in my spit and this morning I had blood in it, now it's brown again. What does this mean?