Lisa,
I just want you to know that you will be in my prayers. This is *not* the way it's supposed to be. Death sucks. There's no way around that. My DH actually preached that at a funeral last year. But since you said that you are a religious person, please know this - No matter what you are going through right now, Jesus can (and, in fact, already has) redeem all of this. It's not your job to hold the family together. Let that go. Your job is to care for your family, especially that sweet babe of yours.
It's ok to be mad at God. It's ok to feel like you've been cheated. He understands. He is holding you in his arms, just like you'll be cradling your new one soon. As much as you'll feel like it, you WON'T be walking this path alone. But it will suck. There's no way around that part.
As hard as this may be, pray about giving your mom permission to just go. You know where she'll be.
I cannot even begin to imagine what you are going through right now. But you are in my prayers. And may God bless you, and give you His deep peace as you both mourn the loss of your mother and rejoice in the birth of your child.