Before I tear down a couple previous arguments I'd like to make my stance very clear. Sex outside of marraige is generally STUPID and if you're Christian also morally WRONG.
That being said I'll state why this is after telling a couple problems I've had with earlier statements.
One, if both have never had sex there isn't actually a risk of STDs.
Two, 16 is definetely old enough to be thinking of "sex, let alone marriage." How old do you think Marry was when she married Joseph? (Or if you're not a believer in the virgin birth, first slept with him?) Most likely quite a bit younger than sixteen.
Three, while the primary purpose of sex is not pleasure, if was for procreation humans would not need marraige at all. It is my belief the primary purpose of sex in human beings is to bring us closer to our spouse and strengthen the familial bonds that help us provide stable and loving relationships.
Four, somebody mentioned adultery and since niether of them are married it'd be fornification, not adultery.
Five, could somebody clarify how it would break the trust in that area of the relationship?
Now beside being stated as an absolute NO-NO in the bible, here are some practical reasons not to have sex:
Namely, you could get pregnant. No matter how safe you are there's still a chance. My science teacher in sixth grade, who was delegated to teach the facts of life to those of us who didn't already know made sure we all understood both he and his wife were using protection when BOTH of their children were concieved. Plenty of ways this could have happened though he didn't mention the specifics. My guess is broken condom and his wife didn't react well to birth control pills. Point is it could happen and that could really screw up your life.
Secondly, an observation I've made from aquatences of mine who've decided to have sex is that they all suffered drops in their grades around the time they started to do so.
Thirdly, there is the remote possibility your relationship for whatever reason (maybe you get pregnant he can't deal with the pressure) may fall apart. And then you'll feel guilty you've given away your virginity to someone whose not your husband and the emotional devastation will be even harder than it would have been. Marraiges, at least to some extent (used to be greater but it's so easy to get a divorce now) encourage people to work through tough problems where merely being boyfriend and girlfriend doesn't quite have as much...attachment? (I want to use a different word, but I can't think of what it was. I apologize, it's 11 at night and I'm kind of tired.)
Fourth, waiting in a major way encourages you to get married (which I gather is what you want) and if you have sex outside of marraige what is to encourage it? What's to keep one of you from deciding it'd be better to wait till after college or when you're in a better financial position? If you've already been having sex, what will keep you from just shacking up instead of getting married? Having sex can lead you down a path you probably would not want to tead.
Now my advice:
If he truly loves you, he can wait a couple more years (as I'll state further he may not even have to). He's waited three already, you're already past mid-way. If he can't deal with it he loves your body more than you, and that sort of person is not someone you really want to be around.
But you do have potential options. Before reading further consider one major question (and then a few minor ones). Do you think you're ready to marry each other now? (I'd talk with him about these questions, by the way.) If so, would your parents approve of it? Are both you parents in support of this relationship? Would they help support you should you get married? (Financially as well as emotionally.) Can they?(Just finacially) How close are you to being seventeen? Do you both do well in school? Can you take care of yourselves?(Chores and things) Have you discussed things like children and colleges and have a good idea of what you both want? In short, if you want to marry each other, could you at this point make it work? If you or he answered no to ANY of these questions, I recommend waiting the couple of years and not even CONSIDER doing the following.
Should you decide yes to them, here are a couple of things you can do currently.
View your (I'm assuming you live in the U.S. otherwise I can't help at all) states marraige laws.(In detail) Most states with parental consent will allow minors of your age to marry each other (and often will do so in some situations without parental consent, though I really don't recommend that course of action.)
Seriously discuss it with your parents. If you work it out it is possible you could get married before turning 18. If it turns out you can't or your parents won't let you I'd still consider the above questions over the next couple of years. Feel free to ask me any questions and I'll try my best to answer them.