My 1 year old Boston Terrier had been doing very well with his housetraining. He would stand by the back door whenever he needed to go potty. He hadn't had an accident in months. But in the last 2 weeks his household etiquette has started to slip. He's had a few accidents in the house, tonight he even peed on the sofa. How can I stop this slide in behavior? What could be causing it? Thanks for your help?

