Ugh help :/

I'm gonna be 16 in a few weeks and although me and my boyfriend don't have sex (never have actually. both of us are still virgins) I wanna go on birth control bc of my period. I'm scared to ask my mom bc she'll automatically assume it's bc me and him are having sex. I've asked her once over text but we never talked about it again. how do I go on the pill? how do I ask her?