How do I talk to my mom, or should I even talk to her, about sex, and the fact...

[Jennifer]

...that I've had it? Today i was sitting working on some art, and I kept having to go pee every few minutes. My mom asked me if I was prego, to which I replied, "Nope! I've had my period since the last time." Now, she knows that I've had sex before, with my ex boyfriend, but doesn't know that I recently have been. I am 18 years old, so legally I haven't done anything wrong. However, my family is very catholic, much to my dismay, and don't believe in sex before marriage. When she found out that I'd had sex with my ex, it was long after we'd broken up. She didn't really freak then, and she hasn't really freaked yet. All she said was that she was disappointed, to which I said, "Well I certainly am not... ;P" haha Anyway, I'm not sure how to talk to her further on this, or if I should. I don't believe in the super strict-ness of the catholic church, and I love my boyfriend very much (to be honest, I can see this lasting quite a while), and I don't feel like I've done anything wrong. I regretted my first time, but I feel nothing like i felt last time, I feel ready. How do I talk to her further on this, or should I even talk to her?