Your question about your son is concerning and it looks like people have given you some good resources for this issue. Two more I think may be helpful for you are:

1. The sermon series Mike Erre is teaching at Rockharbor Church right now. It's on sex and he handles the subject powerfully yet delicately. You can get the sermons on their website rockharbor.org.

2. The second are two books. The first is Sex & the Supremacy of Christ by John Piper and the second is Sex God by Rob Bell. These may not be the best way to reach him but they may help you in your approach and dialogue with him.

However, the reason I'm writing is because while the issue with your son was concerning, your comment about your husband not addressing the issue is alarming. If your husband is a Christian, he should be shepherding and caring for your family like Christ does the Church and like the Bible outlines. Part of that shepherding is fighting for his family (with you, no less!), and being passionate about their growth, their purity, their Christian character. If your husband first of all doesn't see it as a problem, and secondly isn't helping you address it, my humble and maritally-limited opinion is that much of the problem and the correction of it lies in and on him.

As far as how to do deal with that practically, I think you should seek the counsel of older, godly Christian women or a pastor who know you and your family and can steer you straight.

Above all, pray. God changes hearts and the prayer of a righteous man is powerful and effective. (James 5:16)