I am going to have a new sibling at the age of 36!

My mother is pregnant. At first I was like “oh hell no”, then I was confused, then I accused my mother all sort of things. I accused her of leaving my father for another man. Then she opened up to me about the abuse that she endured with my father. I think I saw the signs but I subconsciously ignored… makes me feel sick to my stomach to think about it. My mother is 55. She got married to my dad at 16, and they separated last year. I don’t even know how to process this all. How would I have a new sibling? How would things turn out? I don’t even know what to think anymore. What would people say?