Hello, and thanks for writing in.
Bladder stones are certainly possible, as they are a common cause of bladder problems in dogs, and they are a common source of bladder infections in dogs. I would definitely recommend getting Harry into a veterinarian and having X-rays (or ultrasound) of the bladder done to check for stones. If stones are present, surgery may be needed to remove them. Sometimes a prescription urinary diet may help to dissolve stones, but it doesn't always work.
I hope this helps.