Two kids and no baby daddy

A couple days ago I found out that I’m pregnant, from what the app says, I’m 6 weeks 6 days. I really haven’t had a symptom besides headaches and cramps here and there, now I’m starting to get nauseated. Anyway me and my SO are engaged. We have a son who is 16 months, and my SO told me last night he doesn’t want anything to do with me, my son, and the sweet baby in my belly. I haven’t told anyone. I haven’t said anything because we just had a child not even two years ago. I would do anything for my son and sweet baby in my belly but I don’t know what to do, I’m embarrassed to have to move back in with my parents and raise, not just one, but two kids by myself. I’m having a hard time even telling my mom I’m pregnant. I’m terrified. I don’t know what to do..