asking your mom for birth control pills

Hey! ok so i want to go on birth control for my very heavy periods and just to have control over my own body but here's the thing. I'm 17 & in a new relationship, we aren't sexually active at the moment but im paranoid that asking my mom to go on birth control will make her think we're having sex and lose trust in me/us. how do i go about having this conversation with her? how did you ask your parents for birth control pills? also how old were you when you started birth control? Thanks!:)