My dog pees without warning!?

My dog, a 10 month old yellow lab, keeps urinating on the kitchen floor without even the slightest warning. We bring her out on a regular basis yet every once in a while she will just pee on the floor without a warning. We brought her to the vet and she is on antibiotics for a uti, but she has 1 more day left of it. She will literally be playing or walking around and then it seems like she all of a sudden realizes she needs to pee and squats. I say bad dog when she does it and I bring her right outside. Should I see a trainer?