how to talk to my mom about going on birth control

Devon
I'm 16 and I've been dating my boyfriend for 10 months now and we've decided that we feel comfortable with eachother and we want to have sex. My mom always told me that before I have sex for the first time to come to her so she can take me to a doctor and get me on the pill. But now that it's actually come to that I'm terrified to tell her and I don't know how she'd react. I know there are other options out there like condoms so I wouldn't have to tell her but I'd rather be safe than sorry because I really can't be a teen mom. How should I tell her about it without her freaking out?? Any advice?