How long does it take to completely clear a UTI in a cat...and not see blood anymore?

I am so frustrated, My cat has gone to the vet and is on antibiotics. I have 4 left and it seemed as if she was fine but today I noticed a faint, drop of blood. I am so frustrated and I've taken her 3 times to the vet. He put her on Zeniquin. Could it be the wrong medication? This last trip, Saturday, he also gave her a shot to reduce the inflammation and pumped her up with liquids. She came home and it looked like all was well, Eating, drinking, etc then boom I notice it this morning. Since this past Saturday all was well. What is going on? I am so overwhelmed. How long does it take to get rid of it and is there ANYTHING else I can do besides give her antibiotics. I am emailing her vet today to let him know on her progress. I would appreciate any tips or advice anyone can give me...And what wet food are the most popular with cats, my cat is very picky but trying to get her off dry since I have been reading it is bad for UTI's..Thanks