Dog has wee'd lots in his cage overnight?

My dog is 8 months old and has always been very good at weeing outside. Last night he wee'd twice indoors despite letting him out, had a huge wee before bed and going into his cage. This morning his bedding is absolutely soaked. This includes his new bed plus his old bedding underneath and it had soaked from cage and onto floor. I'm quite concerned but not sure if this is his way of saying he's not happy or something more sinister.