How to talk to my mom??

So I've been dating this guy for over a year now and we've been sexually active for around 8 or 9 months (I'm 17). I've never talked to my mom about stuff like sex or periods or anything super personal so I don't know if she knows or not. But I've been wanting to get on birth control for a longgg time to be safe but I don't want to talk to her about it. Like I don't know how her views are on being sexually active or anything and I don't want to be in any trouble. I know there are places where I can get free BC without her knowing but I also don't wanna go behind her back in taking it without her knowing. What should I do??