my dog had blood in her urine and horrible pain too. one night she crawled up to me and started whining, then i saw bloody urine on the floor. it happened late at night. next morning we were at the vets office and he confirmed my assumption that it was a UTI. she got antibiotics shots for 7 days. after 2 shots she was fine. you will probably have to get your dog to a vet and it's probably an UTI in your dog's case too.