What sort of check up did your vet do on your last visit? Did it include a blood work-up? As long as it was a complete and thorough check-up you can pretty much rule out any health issues, which should be reassuring.
The only other thing that could be causing this issue would be a behavioral change. Has there been any changes in the household? Additional residents of the human or pet variety?
In my experience dogs who have a sudden change in behavior, such as is the case with your urination issues, this change is often triggered by a new addition in the environment and the need for the 'dominant' dog to try and reestablish his dominance by marking his territory.
In addition to using the Housebreaking Pads I recommend getting an enzyme cleaner to thoroughly remove any and all traces of the urine stain and odor causing molecules. A good safe cleaner is
Nature's Miracle. If the scent of the urine continues to exist your dog may think it is okay for them to continue to 'mark' that particular location.