we have had this a few time what we have done and it has worked for us.
1. give the dog something that has your smell on it something old that you dont mind if it gets ripped up and put it where the dog likes to be.
2. leave the room as often as you can for a few min's at a time but still talk to him, then try not talking to him once you dont have to talk to him try staying out of the room for a little longer at a time.
3. this might sound very silly but it has worked for us a good few times of a night leave the light on.
it should help the fact that you have got a settled dog in the house it takes abit of time for a dog to settle into a new home and a dog that has not had a good start to life might take abit more time but stick to it you will win