Fever Two Weeks After Back Fusion

Hi, just had Lumbar back surgery. Fusion of L3, L4, and L5. I had a fever right after surgery from inflammation. I had the surgery on August 28, and on September 15, my temperature suddenly spiked again. The pain got much worse in my back too. My temp went from 99 to 101.8, and has been hovering between 99 and 100.4. My doctor thinks it is just inflammation and common post op issue, but they put me on antibiotics just in case. It was frustrating because I was moving well and felt pretty good, then it all changed. They say with back surgery, it can be very up and down-good one day and horrible the next, because the nerve is healing and reactivating. What do you think? Has anyone experienced fever or sudden increase in pain two weeks after back surgery? I would love to hear other experiences.