I'm new dog owner, i took in my friend's 4 year old shih tzu when he had to move. Its getting cold in the winter and i bought him a jacket. But when the jacket is on the dog he just does't act like himself and won't pee or poop with the jacket on. I have to take it off for him to pee or poop. How do I get him to wear his jacket and act like his regular self ?