UTI in my 7 year old male cat?

My 7 year old male cat has UTI! There were no stones or crystals in his urine but there was a little blood found not a lot just a light pinkish color my vet prescribed clavamox and he is on it for 2 days now and he still have problems peeing he is peeing tiny drops this is really bothering me. He is also on the prescription diet Purina DM because she detected he is borderline diabetic, I only feed him ½ of the can at a time ½ am and ½ PM as she told me to he eats and drink well but always seems to be hungry. Any advice on how long the UTI last and when would he be able to pee normal again? I love my cat dearly and it hurts to see him this way.