My boyfriends mom is crazy! Please help!

So Me and my boyfriend have been together for 5 years (since I was 14) and I just found out I was pregnant! We are both super exited thinking of baby names and preparing. So when we told his parents his mother flipped out and threw a wine glass at me and told me to jump of a fucking bridge and die. She keeps coming over to our place and keeps threatening to beat me till the baby dies. She has never liked me. But this is just so stressful and I can’t deal with it. My boyfriend loves his mom and I can’t ask him to kick her out of our life. I just don’t know what to do. I’m really scared of losing the baby from the stress of the situation . But I also don’t want to ruin his relationship with his mom. I’m trying to be as nice as possible here. Please help!