15 and Not a Virgin, how do I tell my mom?

Taylor
My mom always told me to tell her when I had sex. Of course I promised but I didn't think it would happen this soon. She lost hers at 18 and she expects the same out of me. All these years I've lead her to believe anything sexual is "gross" and doesn't appeal to me, little does she know it does. I had sex for the first time a week ago and I don't know if I should tell her or not, if so, how should I tell her. I would also like to bring up Birth controll to regulate my periods