I used to get them. Cranberry juice is beneficial to prevent UTI's, but once you already have one, it doesn't do any good (other than making you have to pee.)
I saw a dr at Chesapeake Urology for a bit due to them. For a little while, I took prescription sulfur pills to prevent UTI's, and I had an Rx to take every time I had sex.
UTIs are the worst. You totally have my sympathy.