Why do I feel scared about sex?

[A B]

Well, I'm a 15 year old girl. My Boyfriend is 17 years old, we've been together since December 20, 2009. I'm very sure I do love him, so much. So much goes on in our relationship, happiness, sadness, all of the emotions, just like every relationship. The only thing missing is our sexual relationship. I know what you're all thinking, " Your too young to be having sex anyways", but what I've seen in relationships from my school and other students, is that when they have a sexual relationship with their partner, they normally last longer. My boyfriend and I have done things together, but never intercourse, and I think one of the reasons we've lasted so long is because we've done a little more than just kissing. He has never pressured me to do anything throughout our relationship, he's a very trustworthy and sweet guy, and thats how I know for a fact that I do love him, he would never do anything to displease me or pressure or hurt me. I would love to make love with him, not just for fun, but to really connect, and when I think about it I feel so good about it, but when I feel like I have the chance too, I get a little scared inside, like my mind is telling me to wait till we're older and married, but I still want too. I just want to know why I have both of these emotions, and which one to follow. Don't answer from your mind either, answer from your heart, and forget about age differences please. I just want to know what you would do in my situation, if you truly loved someone and you really would do anything for them.