You really really need to get a professional into your home to evaluate and discover the root of your dogs aggression/insecurity with the baby. You need to do this tomorrow. No waiting.
I don't want to sound harsh, but your babies security is paramount. And someone needs to actually see the interaction to determine the cause and recommend if it can be fixed.
No one on this board is qualified to help you based on a web posting. This situation is possibly too dangerous for internet help. Sorry.
Good luck and congrats on the baby!!!
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