Then he's reacting to something that you are doing and his peeing is likely fear-based or stress related and is called submissive urination. Don't pull your hair out just yet - most everybody has fits and starts when housebreaking. Dog's don't empty their bladders out of anger but do when the bladder is full or they are marking their territory for other dogs and some do when they are stressed or scared. There is likely something that you are unwittingly doing that he's associated negatively for some reason. I would change things up and sort of restart his housebreaking from scratch on a strict schedule and with lots of positive reinforcement. Perhaps you could read up all you can on Submissive Urination and Behavior Modification training techniques and sort of retool your relationship with him. Lots of patience and love and gaining all the knowledge possible on these subjects can go a long way sometimes when we have setbacks in housetraining. Those would be some of the things I think I would try under the circumstances and good luck to you.
