New Dog Ownership/Odd Dog Behavior

Question
I just adopted a 5yr old cocker spaniel yesterday.  He is actually an exceptionally healthy dog(AKC/CKC, 5th generation pedigree, etc), but has been used as a stud dog in various "puppy mills" his whole life.  He has always lived in tiny cages and has never known what it is like to be loved and not mistreated.  We want him to eventually be able to learn to be a "normal" dog: to know that our home is his home, to play with the kids, etc.  But since we got him, he hides from us all day, refuses to eat anything, has not pooped, and gets so nervous he urinates a little when we try to get close to him.  Is this normal transitional behavior?  How long (on average) does it take for dogs like this to begin to act normal?  At which point should I begin to worry about him not eating?  What steps can I take to help him?  I know I have only had him for a day, but I already love this dog, as do my husband and children.  I won't give up on him, I just want to know what I am getting into.  Any Advice?  Thanks.

Answer
Hi Michelle,

This may be a really big pill to swallow:

He may always be like that. A puppy mill puppy who has been in a box his whole life will have little or no coping skills for the stress of a new life and while he may improve over time any new stress will most likely send him back to what you are seeing now.

Give him a  small quiet space with his food and water and a bed and once he is comfortable there (if he can get comfortable there) gradually give him more freedom. He is overwhelmed by all this new stuff. Is it normal? Normal for a puppy mill puppy yes.

If you keep him, know that it could be a long haul with very little improvement. But if your goal is that he be "normal" then you may want to reconsider.

I wish for the best for all for all of you.