Ask him some questions: What would he do if a girl started coming on to him and he didn't love her? Maybe didn't even like her but thought she was sexy? What if she was drunk? What would he do if he saw some other boys messing around with a girl who was drunk? What if it seemed like she liked it? Would it make a difference? Would he say anything? What if the boys were his friends? What would he do if a girl liked him and wanted sex with him and he wasn't ready? Does he think that if a girl had sex with him, she might be more inclined to think she was in love? How would he know she was only with him? What if she offered to send him a picture of herself without clothes? Does he know anyone who got a girl pregnant and what happened to the boy? What would he do if that happened to him? What is important to him about love? What would he do if his girlfriend made him really, really mad? Who would he talk to?
There are so many questions that a boy needs to think about. He may not want to talk to you but that's OK. Ask the questions. He will think about them in his own time and and probably to some loud crazy music. But if you are very quiet and very available, he will probably come in some day and plop down and say, "You know, I was thinking about that thing you said the other day...."