How to ask mom for birth control

I am reading to lose my virginity, to my best friend, my boyfriend, the person I trust the most in my life. He is very important to me and we are both ready to take that next step in our relationship, a new special way for us to connect. I was thinking about birth control and don't know how to ask my mom.. She is a very religious person. I however am not. She wants me to wait till marriage or at least 21. I don't want to wait. I am ready. How would be a good way to ask for birth control? Answer pls!! Also, saying it regulates your period, isn't gonna work, she's not an idiot.