There's a very old WWII-type axiom that says, "Why buy a cow when you get free milk?" Of course, the implication is "Why marry a girl if she'll have sex without marriage?" There is some historical validity to this view. More recently, especially since the onset of birth control, this seems unnecessary, since sex can be enjoyable for both people, with the danger of pregnancy mostly gone.
Strangely, among less-educated females, there's been a drastic rise in out-of-wedlock pregnancies. But that's a statistical factor, and may not apply to a single individual- you.
I think those rules were right for your mom. There's also a chance that she *wishes* she'd lived by those rules. You may never know, since any mistakes she's made as a young woman might not be ones she would share with you.
Being in a relationship before marriage will work for some, won't work for others. The choice is far too personal, with far too many variables to say, "Go for it!" or "Be chaste!" The choice will be yours. If you're relatively new to dating, I'd recommend going a bit slower in your decision. For some folks, a first-date sex event is fine. For others, you might be happier to wait a long, long time.
This is a topic you can discuss with the one person to whom your decision makes more difference- your boyfriend. It's one thing to be "easy," and it's another to be "frigid." The two people who will decide don't include anyone here on Y!A or your mom. Think about going slow, but make up your own mind. ... Good luck!!!