Pick up some cranberry capsules at the drugstore on your way!
You can start to mix cranberry into Gunner's food right now. (It's tangy, but he should still eat his food if you add a bit of warm water). It won't harm him and if he has a UTI will definitely help him.
could be a uti; s/s are frequency, burning, abd/pelvic discomfort, odd odor to urine, blood in urine
could also be a prostate issue if gunner is a male, esp if he's older;
could also be new onset of diabetes, bladder stones
these are the most common ones; i agree w/all who've posted prior to me; he needs to go to the vet; and bring a clean catch urine w/you; one that's fresh, no more than an hour old so the vet can analyze it
To add to Ellen's last suggestion, my vet always insists on first catch of the day. It's most concentrated, so it's the best to analyze. If your appointment is later in the morning, you can always stick it in your refrigerator (properly labeled, of course!).
I know, we're kind of giving you conflicting advice. So, if you have an afternoon appointment, talk to one of the techs (not the receptionist) and ask what the vet prefers, a fresh catch or first catch of the day that's been refrigerated.