Do I have pneumonia, bronchitis, or just a cold?

Last Thursday I got a cold. I was coughing really badly and was sick until about Saturday when my fever broke. But my cough persisted. I was coughing really badly until Tuesday, when things started to get better. I thought everything was good by yesterday. But today, I have a sore throat, a headache, and, overall, I'm very tired. It feels like I'm getting sick again! I don't understand what's happening to me! I've always been sick a little longer than normal people, but never this long. I visited the doctor on three occasions several days ago, and they said my chest was clear. What's going on? Thanks