It’s the most common cause of frequent peeing. Bacteria infect your kidneys, bladder, or the tubes that connect them to each other and to the outside world. Your bladder swells and can’t hold as much urine, which may be cloudy, bloody, or strange-smelling. You might also have fever, chills, nausea, and pain in your side or lower belly. Your doctor will likely prescribe antibiotics to get rid of the infection.