Is your dog spayed?
Sometimes as god get older their estrogen levels lower (just like in people) and if the dog is spayed and they have this issue it can lead to the bladder muscles being a bit looser then normal and cause her to "leak" it will often happen when sleeping. This issue can easily be fixed with a small pill of hormones, from the vet.
A bladder infection might be urinating alot, in small amounts (sometime the urine will have brown/red color to it as well)
Either way it's a good idea to get her to the vet as soon as possible, to find out what the issue is and to keep your house free of urine!
Best of luck!