Seeing boyfriends mom today and I'm terrified pls help

Hi guys.. so I'm seeing my boyfriends mom today to talk about our baby. I'm 21 week and haven't seen her since a month before I got pregnant. My boyfriend and I are both 17 we've been together since we were 15 and obviously got pregnant on accident. We were using birth control and protection plus I was told I wasn't ovulated. But I was, I just ovulated two days before my period was supposed to come. We were safe and really shocked I was pregnant. I told my parents right away cause I'm very close with my parents. But my boyfriend wanted to wait to tell his parents so I respected that. But he waited four months to tell them 😑 I decided to tell them myself because he wouldn't. They obviously freaked out but just on me, not him. I didn't care it was whatever. I just took it. But then my boyfriend told them he wanted to move out in the summer with me and his mom completely freaked on me. She threatened to call cas (they're already in my life so idk why she would) she wants a paternity test, even tho I've never had sex with anyone else. And she threatened to call the cops on me. Now I can't live at home cause it isn't safe for me or a baby which is why cas is in my life. So I really have no choice but to move out unless I want my baby taken away. So I told her this and told her it was his decision to move because he's old enough. Now she hates me. She said some pretty mean stuff but I didn't reply cause I didn't want to argue. Now I'm seeing her today for the first time to talk about stuff but I'm so scared. I feel like crying and I don't even want to do it but I have to. Anyone have some advice to help me calm down because I'm so terrified and stressed and I don't want the baby feeling this. Please help