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Cary is right on both counts.
You don't have to demonize sexuality or shame your son or the girl for doing what comes naturally-- but do have a discussion with him regarding the practical consequences and necessary precautions. Talk to him about his future plans, how he can protect his plans, and how he can employ self-respect and respect for his partners as a gentleman.
It is a myth that all men refuse to wear condoms. Nice, good men do wear protection and can enjoy themselves while not putting their partners at risk for an unwanted pregnancy or std.
It is okay that you personally feel awkward about his having sex and don't want your son doing it in your home. He is still a dependant teenager after all, not like a grown man in his 20s who is bringing home his fiancee at the holidays.
There is something just too weird about parents and children being comfortable with each other's sexuality. There is no need to push it.
I remember very briefly dating a guy in college who introduced me to his father very early into our experience and it was very clear he was showing me off to his dad as a sexual conquest rather as a girl he was dating. The "relationship" lasted about 30 seconds after that because I didn't feel I had his respect and the idea that sons would try to brag to their dads about their sex lives grossed me out on so many different levels.