[matese]

Welcome to YT, 4 months old small breeds can't hold pee for long period of time due to small bladder. Holding it at night could be 1-like ilovejoel wrote, doesn't want to soil his sleeping area. 2-Also, when they are sleeping, they are not active and drinking water, so can hold it longer. When I had puppies I first trained on paper in doors, at 5 months old they were 100% paper trained with no accidents, then I started the house breaking training. They were fed and walked the same time every morning, then off to work I went, returned home at 4:30 they were walked again. At 7 months old they were 100% house broken. Try taking him out more often, but, it MUST be the same time every day. Consistence and patience are the key words. Even if he does not pee or poo when you take him out, stay with it, same time times every day, he will get it.