Annoying mothers.

Okay. So I am 18 years old, and I have been dating many boyfriend for a little over a year now. Being raised in an honest family, I told my mom that I would likely be sexually active when I turned 18, (February 8th.) And I have, I've been responsible with my boyfriend and we use protection every time. But each time I ask or say I'm going over to his house, my mom always has something to say about waiting till marriage to have sex. She is a Christian, mind you. Which is funny, because she waited to marry my dad then to have sex, because there's some statistic that says people who wait to marry before sex will have a more successful and long lasting marriage. But she and my dad got a divorce a long time ago. So that theory went to shit, and I don't believe in it. I feel I am old enough to make my own choices, but how can I make things normal again? I don't want her attitude every time I say I want to go over. Why can't she get over herself? Honestly, I don't care what she thinks about me and my activities, but it's annoying quite frankly. Can anyone shed some light?