We Have A 7 Year Old Miniature Schnauzer That Sleeps

We have a 7 year old miniature schnauzer that sleeps on our bed and has wet the bed at least 3 times in the last month. We take her for lots of walks through out the day, and make sure she goes out before bed. Lately she has been waking us up during the night to go outside. She has been drinking more water as well, but she plays a lot, she shows no signs of any kind,and her urine looks clear. We have been using Denta Sure on her teeth and wonder if this is causing a problem. Have you heard of any similar problems,