What Causes Fever,rapid Pulse And Extreme Fatigue?

Are all types of pnuemonia evident on chest x-Rays? I had laser prostate procedure three days ago and went to the E.R today with fever, rapid pulse, and extreme fatigue. My blood oxygen levels were slightly low, but I did not have a cough. Chest x-Rays were clear. I was prescribed Ciprofloxacin for UTI, indicated by urine examination. I was also prescribed Cefdiner, and the pharmacist indicated that is usually for respitatory infections. Does it appear that I have two infections?