i think the problem is your dog believes that you dont want him anymore. He just afraid of that.
Just spend more time with him. Talking with him even he couldnt understand. But he could feel you still like him.
And take your dog go out. Playing with him.
I wish your dog could be fine.
I will leave my sweet heart for 3 weeks( i should go back for holiday). And now i am trainning her sleep alone....but she is very strong mind....must jump on my bed .....
i start to worry about her...