these are things i've heard that might help you and your baby
one thing you can do is to work with you puppy by leaving the house, and telling him to wait, close the door, and open it again, and telling him 'good wait' (or whatever word you think works for you) repeat this, and each time you lengthen how long before you open the door. basically the idea is to get him use to you leaving and coming back, so he knows that you will return and he doesnt need to freak out.
the other thing i've heard is to not make a big deal out of leaving and returning, you want to make the dog think it's nothing big, and it's just something normal you do. with that method. you just leave the house without interacting with the dog, and when you return, you don't make a big deal out of it either, you wait 5 min. before you acknowlege the dog.
i don't do either one....lol. i usually just prepare a dish full or treats cut up into little pieces, and sneak out of the house while she is eating the treats....