What can I do now to avoid this happening again?

I had a UTI about 2 months ago. I went to my doctor and he prescribed penicillin-based medication, which I took for about 15 days and it went away completely. I followed the treatment cycle fully. I am having symptoms again now, everything except the bloody urine but I am guessing that's coming too. Should I go to the doctor for another round of the same medication? What causes UTIs to reappear? I don't know why it's back now. What can I do to avoid it happening again?Thank you