My 6 mo old female boxer has to urinate every 10 min. We have tested her for everything from a UTI to diabetes?

She will go in her kennel if she is in there more than an hour and go on our floor if we don't let her out right away. She has no other housebreaking issues. This is not an issue of not housebreaking properly because she goes to the door every time and knows to go outside. It just seems like she can't hold it. Help!