I love this article. I'm a devout Catholic but I don't believe pre-marital sex or cohabiting after engagement is sinful. I've tried to understand the argument of waiting, but seriously, after the age of 25 and after dating for many years, if you can stand to stay away from each other physically I think there's something wrong with the relationship. So yeah, the article below is very eye-opening, especially how the Catholic teachings weren't always the way they are now! Hmmm....
"The first sexual intercourse between the spouses usually followed the betrothal-a fact of the Catholic tradition that has been obscured by the now-taken-for-granted sequence of wedding, marriage, sexual intercourse."
http://www.uscatholic.org/life/2008/06/a-betrothal-proposal