Yes it is a dominant behaviour but bear in my that your dog is only taking advantage of a situation - it is not challenging you for overall control here. If the dog totally believed the relationship between you and it was as you see it the dog would not get on the bed. It may even be that you are welcoming the dog in your sleep or, more to the point, your dog believes that you are welcoming it. Maybe you turn your back on him when he gets up so signalling that his prescence is not objectionable.

I have never come across a case of seperation anxiety that was not linked to the dog's status in the eyes of the dog. I have also never had a case that was not eased by taking the responsibility off the dog of being the leader. The only dogs I don't consider cured of their anxiety are the ones that have improved so much in their owners eyes that the owner is over the moon, happy as can be but refuse to go any further with a dog that they consider cured. The most infuriating thing I have heard on many occasions is when I comment on a behaviour the dog is still showing and the owner says, "Oh well, she's always done that!"