I don't think sixteen is too young. My boyfriend and I were sixteen when we got together, and we've been together for nearly three years now. The only advice I have for you is, never settle. If he's good to you, and you love everything about him, then that's not settling. If there's something about him that bugs you though, and you don't want to break it off with him b/c of having been with him for so long, then that's settling. That's what makes for a very unhappy relationship. Best Wishes!
Best Wishes!
--Nomad