25yr old low back pain fever headache- go to er neg kidney bladder inf stone norm wbc-er 3 day later, amox as precaution- er 4 day later sore throat?

Virus?: If the pain is across and involving the hips / pelvis (=very low back), could be part of the aches associated with a viral infection, particularly since er eval sounds negative for anything worse. In that case, should improve with Ibuprofen or Acetaminophen and the resolution of the viral infection. If persists, primary dr may need to do more testing.