Pregnancy anxiety

I’m newly pregnant w/my 3rd and I am so anxious about it I can’t function. I just have this deep feeling of regret and so badly want to not be pregnant. I’ve been pleading with God and I can’t kick the feeling or anxiety. We are a very stable family, there’s no reason for me to feel this way and I feel so so guilty. I also have some low back issues and I’m terribly afraid of what pregnancy may do to me.