[quote="twoangels, post:10, topic:212558"]
I think another thing to consider is what chastity means. Do you mean that you're just avoiding as they say "going all the way"? I think its important to remember that marital intimacy is more than "all the way." Not only is it very easy to eventually fail to say no, but its also easy to succeed at this through developing mental habits to supress and reject the way God designed human sexuality. We need overall to respect the fullness of the gift of our sexuality. Driving down with the petal to the metal with the emegerency break on and your left foot on the other break isn't the wisest thing in the world to do even if you do succeed at avoiding running the red light. It is important to remember that as intimacy builds in the relationship, you will have to rely on the break and may even have to slam down on the break really hard, but you shouldn't be having to rely so heavily on the break, as if you get credit the more times you resist intense temptation. You should be avoiding that temptation as much as you reasonably can.
Then as other people explained, there is the concern of causing scandal.
What does seem to be unsaid is the importance of emotional modestly. Saving sex for marriage is a part of that emotional modesty. Chastity just isn't all about frowning on sex before marriage. In a way, it is reserving marital intimacy found in more forms than just sex. Its that intimacy found in waking up next to each other, that intimacy found in the sharing of chores, in being a part of each other's bedtime rituals. Its really reserving married life for married life. Its really a part of being able to say after you've been married that truly your life has drastically changed in more than just "Oh now I get to have sex."
I'm not saying you can't enjoy each other's company or share fond memories or to share anything special together. Its not just "ok let's stay in cold water and then when we get married we'll jump into the hot tub." Its rather enjoying the relationship where its at, and giving honest expression to where it is at.
Plus, having sex isn't the only sin against chastity that you might be tempted to do due to the situation. You don't even need to remove your clothing to do some activities that are not appropriate for unmarried couples.
[quote="ForAll, post:11, topic:212558"]
As several other posters have pointed out, even if you don't ever have sex, it is wrong--even beyond the scandal that you are giving to others.
I assume you understand that not having sex, as with refraining from all sin, is about maintaining your purity: of heart, of soul, of body. Purity is not just a "line" of physical involvement to be preserved; rather, it is a habit and an attitude that affects all of your behavior and your thoughts. In that way, purity is inextricably linked with modesty, that trait of veiling what should be sacred.
The Catechism is particularly instructive here:
Although this is speaking primarily of modesty in dress, I think it applies to this situation as well. Modesty is about protecting your inmost self, and recognizing that what you do with your body affects your soul--and so, in being comfortable being more unveiled to your boyfriend, bodily, you are in fact sharing with him what should rightly be hidden.
Patience and moderation is preserved in this case by recognizing that sharing a bed is not given to you at this point in your relationship; that is preserved for marriage, because we recognize something holy about the marital bed--the bed a man and a woman share.
As for more practical considerations, why do you even have to sleep at his place at all? Even THAT is giving scandal, and offending your modesty. If it is too late for you to drive home, then you need to think about that in advance--either cut your dates short, or see each other fewer times a week. Try reading T.G. Morrow's Christian Courtship in an Oversexed World--he gives these issues a full airing.
If you still do not understand, I want you to think about what would make a couple "married" in terms of behavior, for we who are Catholics: sex, mutual children, sleeping in the same bed, living in the same house, seeing each other every day, sharing most meals, talking every day, etc. Now take away those you would also do with an opposite sex friend that maybe you have classes with every day. What do you have left? Sex, mutual children, sleeping in the same bed. Those are aspects of that relationship that should be reserved for that relationship, because they are appropriate to that relationship and that relationship only.
I was going to post but I read these two last posts and they said it better than what I was going to try to say.