My Siberian husky is becoming un-house trained again.?

So we have a 2.5 yr old siberian husky. He's been neutered because we have a female dog too. He was fab at letting us know he needed to go to the toilet. He'd come and lick us then go to the door, if he was real desperate he'd jump up at the door. Never once did he have an accident! Lately, many the last 3 months, every morning when I come downstairs, he's pee'd against the bin or the wall, sometimes he poo's too. The dogs sleep in the kitchen, and it's very possible for them to run and wake us when they need to go outside. The female is fine she would never pee inside. What is wrong with our sib? He is let out last thing at night before we go to bed and it is really doing my head in because we have a little toddler too and I'm pregnant again and the smell really ugh, just doesn't bare thinking of!!!!