aww well done!!, my son had a rescue rottie who was just the same, we once took her to the beach and was out best part of the afternoon and she never weed she was so bursting she was whimpering on the way home in the car we eventually stopped about a mile from home and i walked her home, she kept stopping to squat but then was too afraid to go, it took her many months but she will happily go now but doesnt really squat she sort of goes on the hoof so as to speak bless her