I Have Had Persistent UTI, And Kidney Stones For About

I have had persistent UTI, and Kidney stones for about 3 going onto four years now. These all started and occurred before I was sexually active, I had an ultrasound on my kidneys nothing was wrong, I have gone to the urologist and taken cranberries,cranberry pills, reduced my sodium and processed foods intake and drink lemonade. However I still have very severe and reoccuring kidney stones, what do I do? And what's causing this?