Conflict of emotions

What happens when you cross an exhausted mama 39 weeks pregnant high on emotions with a tired 3 year old high on emotions? Conflict.
I'm crying out to God - I don't know if I can do this thing called motherhood.
I'm afraid I'm damaging my daughter.
Today I lost it. I screamed at her. I had to leave her so I wouldn't do or say something I'd regret.
And she just came after me, crying hysterically and screaming and what did she want? She wanted me.
She just wanted me to come and lay down with her.
I didn't. I couldn't. After laying with her for over an hour trying to get a nap out of her and get a much needed one myself, I just couldn't. And now I regret it.
She's upstairs asleep after passing out from sheer exhaustion and emotions I'm sure.
And I'm downstairs crying because I feel like I'm a terrible mother.
Can I do this? Really? And another one can arrive any day now? How do I do this?
God! She's your creation and I just screamed at her. The way my mother screamed at me countless times. I don't want to be this mother.
I want to escape. And I'm trying so hard not to escape.
Parenting isn't for wimps. I'm feeling pretty wimpy right now.
When that baby is born you have no idea how hard it's going to be. Hard labor? That's nothing compared to what's ahead.
Perseverance. Just breathe. Just take it one moment at a time. Draw close to God. He made her. He made me. He knows.
Like the first bible verse she's memorized: God is with you wherever you go.
God is with me. Every day. Every moment. Even this one.
Please forgive me. Help me start over.
Your mercies are new every.single.morning. Every.single.moment.