Since Sunday morning I've been having back pain (it's not severe), it hurts just below my ribs. Sunday night I got a low-grade fever. My temperature hasn't gone down from 99 degrees ever since, and every few hours my temp goes back up to around 100.5. I also have a very bad cough. I went to my doctor yesterday, he didn't tell me what it was, he just told me to take some advil for the back pain and prescribed me some zithromax. He told me that if I"m not better by Friday to call him. This morning when I awoke my back pain is still there and now i'm experiencing a lil bit of pain in my lower back on the right side around my waist area. What could I possibly have? Should I wait till Friday to call my doctor or should I call him now and tell him that I'm having back pain in my lower back? I'm getting a little bit worried because I'm afraid it might be a kidney infection, which my mom had a couple of years ago and she had to go through a lot at the hospital and had her kidney removed. Anyway thanks for any help.