I have a dog - 2 years old - house trained, but only (it seems) during the day! He will either let himself out, or bark to be let out if the door is locked! However, at night, despite me letting him out before I go to bed (around 10.30pm) he still does at least 2 huge pees and a poo indoors in the night. This is practically EVERY night and is really pissing me off now! Any ideas? He doesn't bark to go out, or make any sound at all.