Can a uti do damage to your body if you've had one for awhile but haven't known?

UTI: Most infections especially bacterial that cause UTI are not silent. You will feel symptoms. In general untreated infections are not the best thing for your body. Untreated bladder infection would not be asymptotic. There are some low grade chronic infection that can be undiagnosed. Talk to your MD. A simple urine test and a complete history and physical should point out an infection.