Am I Too Young?

I am 19, my man is 19, and we are engaged. He's in the military. A lot of people I don't know tell me I'm too young and don't know the story. We have been together since the crappy age of 15, and have been through thick and thin together. He's my best friend, we were each other's firsts and we did so much together to help each other grow. There is nobody else I have ever or will ever want to be with. He is the one, and I'm excited to spend the rest of my life with him. So, am I too young? I don't think so. I don't want to "experiment with other people" like I should, according to others. I see all these bad relationships based on mistrust and pettiness and I'm grateful I have something above that.