If you're thinking about getting married at any age, think and answer these three questions: 1. Will he be able to support me and our future family? 2. Does he have any potential of leaving you? 3. Am I willing to get in bed with him every-other night?
I don't think that there is anything wrong with marrying your boyfriend whom you have been together with since sixth grade. I think he is the right person to marry since you know each other for quite some time now. However, you should consider other factors before you decide to get married such as finances.
I think you might be to young to marry. Trust me there are a lot of guys out there that you might want to explore. My parents married at a young age & they've had a lot of problems because they never got the chance to explore other people but hey if you want to go for it do what you feel just do what'll make you happy :)