I don't know if you already have done this, maybe you have, but have you both sat down and spoke seriously about this and how you both really need to take things at a slower pace, he needs to be made seriously aware of how you really feel about getting married before you are 20, you both have your lives ahead of you to live, and if he will feel the same or even you for that matter, in a couple of years then maybe it will then be time, but at this point in your lives you need to experience things, start your careers and/or college, it is harder but not impossible when your older to these things such as go to school, etc. I did that later in life with some regret, keeping house, caring for a kid in grammar school, and driving out to college classes (not to mention the homework) and this is just half of what I was doing, it can get overwhelming carrying a heavy load. It is ideal to do these things while you are young, single and not having to try to care for a family. You both may need to double think your priorites at the present, cause if not your future(s) may be compromised down the road of life.
Best wishes for you both
"darkeyes"