Starting Birth Control

I think I want to ask my mom about going on birth control but I'm afraid. I don't want her to think I'm having sex, because I'm not at the moment but I just want to be ready in case I decide to. Having to explain that I'm pregnant seems a hell of a lot harder than explaining I want to be safe but I'm still afraid to do it. What do I say so it's not like, awkward or makes her mad?