Advice please!

I am 17 weeks pregnant and am worried about telling my mom. My boyfriends family are ecstatic! They can't wait, but I know my mom won't be happy. Due to issues years ago about her making me get an ...abortion when I got pregnant at a young age, as well as her currently taking care of my sisters child due to her getting into drugs and being unfit to take care of her own child. Anyway my mother is loving but crazy, she is an alcoholic and feeds on drama. I can only imagine what she's going to say and try and do when she finds out. My mom's famous line that I can remember that she said to all of her kids as well as me is, "I swear to God I will make your life a living hell." or "You are dead to me." I can't deal with the stress she will bring upon my life. I have to much positivity going on around me but the weight of this on my shoulders is bringing me down. My boyfriends family say they don't blame me for not wanting to tell but I need advice please. What would you do?