Congratulations on your newborn!
I don't have kids so I'm kind of useless here. I just wanted to tell you to have patience with your furbaby. He got all the attention before the baby and it's hard to have to share mommy. Give him time to adjust. Don't give up on him. Maybe taking him to obedience classes for a refresher (and alone time with mommy) will help him get back to being his usually adorable self.
I'm sorry I can't be more help!! I wish you luck!! Hope it all works out!