To some degree at least, I think your fears may be normal. I remember thinking about many things that could go wrong when I was pregnant. But everything turned out fine. i'm sure your therapist has heard much worse than what you're saying. If you trust her/him, open up to her/him. Your anxiety and stress could be hard on your children, too. If you need to leave the kids with a family member for a few hours so you can relax, meditate, or work through some issues, do it!
Fear is crippling. You are not really "alive" if you're fearful all the time. If it would help you to pray, don't worry about it. Do it. Do whatever (as long as it's legal and moral) you need to do to feel better. Your therapist should be able to help you figure out the root of your insecurities. Do you have worries about having enough money to support yourself and your children? Are you anxious about the well being of your children?
Best wishes. Take care of yourself.
Mum