how do I tell my mom?

Sarah
I'm 17 turning 18 ,my boyfriend is 19 turning 20 in 3 months. So before I get any rude judgments yes we are both financially stable. We both make approximately 3,700 monthly. I've been living with him for about 6 months now. So I just recently found out Im 4w and 5 days.the problem is that My mom and I aren't in good terms, I'm scared to tell her I'm pregnant. I don't even know what to say... can you guys help me out a little?