Hi There! I Am 45 Years Old And I Was

Hi there! I am 45 years old and I was recently treated for a UTI, however since completing my antibiotics, I have developed lower back pain sometimes shooting into my hip and bum. When I lean forward in a sitting position it puts pressure on my bladder and causes moderate pain. During a recent internal test my doctor pressed on my bladder and it was very sensitive. I am going for an ultrasound but not until March. Any idea what could be causing my discomfort?