Yep...bladder infection or urinary tract infection or kidney infection all pop into my head. The doctor can usually diagnose from a urine sample, nothing invasive. You do need to get antibiotics if you have one of the above, they don't go away on their own and tend to get worse. In the meantime, drink lots of water and cranberry juice - they both help. I get chronic kidney infections, it is not something you want to ignore!