Friends with benefits?

A long time ago, a boyfriend and I broke up. He was really kind, caring, but the downside is that he smoked weed, and drank. It was a bad influence for me, so I kind of ended it. Recently, we got back together, him begging for me. I agreed and we stitched back together our relationship. He is still the same 'ol bad-decision making kid I know, but I love him al the same. One day, he called me and said, "I don't think I want to really be with you." He explained that he wanted us to be "friends with benefits." when I asked him what he ment, he replied, "Sex." I'm a virgin, but he doesn't know that. In fact, he thinks I'm not, based off of information he's gotten from others. He says that he wants to fu** me, but just a as a friend. I angrily asked him if he was just in it for the sex. And he just laughed. So, ovbiously, he is. But suddenly, I want to give him what he wants. Would it be utterly wrong to have sex with him? To tell the truth, I am not that close to becoming the legal age at all...what should I do? I don't want to lose him, although he is a jerk, kind of. I probably sound like an idiot, but I need help.