Seeing that he's still a teenager, you have to give him some space to figure this out. His reclusive attitude is probably the result of your family's religious attitude towards homosexuality. When you talk to him, try to take a neutral stance and genuinely try to help him figure out his sexual orientation. If he feels that you are trying to push religious ideology on him, he will become even more defensive.

Regardless of the choices your son makes, never forget that he's still your son. You obviously love him and to treat him differently because of his choices would be unfair. Don't try to 'change' him or explain how his choices may be 'wrong', he'll feel oppressed and lonely and likely become depressed. These years are some of the most important years in his life when it comes to establishing a life-long relationship with you. Don't let your son's uncertain sexuality effect your relationship with him. And if someday he decides he's bisexual or gay and happy with it? Keep in mind that it's his personal life, not yours, and be happy for him!

He'll figure it out on his own, you have to realize how he's feeling so take it easy on him, and you know no one can give you real advice on this situation, he's your son, love him for whatever he is and see it through his eyes.

It sounds like he just needs the time and space to figure things out for himself. Let him know that you're there when he's ready to talk and then leave it up to him.