5 year old dog having accidents at night

Hi all,

My 5 year old male dog has all of a sudden started having accidents at night. He is perfectly fine during the day so I’m not sure what the issue is. I go to bed pretty late and will take him out for the last time at around midnight, then just a few hours later i will hear him barking after he has had an accident. Given the relatively short space of time since being taken out, i find it hard to believe it is because he couldn’t hold it. He usually sleeps in the office but I’ve noticed when we let him sleep in our room, he has no accidents. Could he be having accidents because he’s stressed to be sleeping alone? He was fine before so I don’t know where this could be colour from. Would be grateful for any suggestions.