I DON'T even want to ask if he's had sex. Although I don't think he has, but I'm afraid to ask just in case the answer is yes, because I'm not sure I'm ready for that. He's a pretty good kid, and doesn't usually do things to "shock" me.
So many things, and I am probably not the best one to articulate on this, but I will try.
This is not about you. This is not your fault. You did not "do" this.
This is about your son. If he knows the words and uses them correctly when reffering to himself, then it is very likely he understands what he is saying to you.
You're afraid to talk about sex with your son? You can not afford to hide from this issue. You need to make shure that he is safe (safer). You owe it to him, and you owe this to yourself.
I think it would be reasurring to him for you to thank him for being open and honest, as sharing this kind of thing with a parent is not easy, even at 27.
Who knows, maybe this is just a phase. But as he matures and he becomes the man he will be, he may go more towards either end of the spectrum.
I do not mean to sound preachy or judgemental at all. I went (am still going?) throught this mostly on my own. The coming out process for me was somewhat adversarial, but has settled down now. I think you have a valuable opportunity to work with your son, and help him be a well adjusted, happy human being.
I wish you the best. If you want, I am open to PMing or speaking with you.