“Why am I committed to this in the first place?”

Because I have periods where I want nothing to do with God and I'm angry at him, I have periods when I completely ignore his existence, and I have periods where I'm overwhelmed by his love and forgiveness and continued patience with me, even if I've just been allowed a taste of the natural and spiritual consequences of my sinful states of mind.  These three states directly impact how I behave towards women and how I view sexuality.  

1) When I'm angry, among other things I use sexuality as a weapon of rebellion against God, my legalistic upbringing, restrictions, rules, etc.  In my relationships, I become a lascivious, conniving, secretive, manipulative, extra-manipulative, super-manipulative, vengeful asshole.  And I'm scarily good at pushing things further and further and getting away with more and more, mentally and physically, alone or with a girl.

2) When I'm apathetic, I just go with whatever I feel like at the moment, or whatever my girlfriend at the time wants to do.  Regardless of whether those actions are moral or immoral in themselves (I hate gray areas), my motivation in any case is selfishness, as I simply don't care about what God wants or what is best for the health of my relationship and the physical, spiritual, and mental health of my girlfriend.  Ironically, sometimes this is when I'm my most sinful in this area, and yet doing the least amount of physical or thought-based sinning.

3) When I'm actively walking with God, all the questions about "Is this too far?" and all the debates and justifications and alterations and setting firm black lines every two weeks, all fade away.  As in, never happen anymore.  Instead, even while I'm making out I can feel the Holy Spirit's presence within me, and within my girlfriend, and it creates a more intimate and fulfilling experience than has ever happened when I've "gone too far."  And when we're not making out, I can still sense him in my soul, not as an unwelcome presence or as Big Brother, but as my trusted and loved friend and ally, the one Person I long to please most.  Then, the "good behavior" comes about as a natural result because I don't have to worry about "how far is too far" when my actions are being guided by God and my desires for him exceed my desires for myself or my girlfriend.  I'm still a virgin, but things can and do get hot and awesome during these times, and more satisfying short-term and long-term. Oh, and I also become a much more attentive, loving, leader-like, and caring boyfriend.

So why am I committed?  Because I know who my redeemer is, and I know that he is very real, and I know that when I'm with him, he turns me from the despicable douche-bag I naturally am into his son.  Because feeling God's pleasure without legalism is like having your cake, eating it too, and sharing it liberally with everyone around you.

Oh, yeah, and ditto Kaitlin on the healthy Christian sex education bit.