I "stopped growing" at 16 also. I was 5'4", 105 #'s.
At 21-- 5'6", 120 #'s. I think your body just naturally has this growth spurt. (Most of us do anyway) Just think for minute- How many folks do you know that look the same now as they did in High School? And I'm not talking about aging either. There is a transformation from being a teenager to a young adult. Every thing else is just getting old! LOL!
I also wanted to give you a "heads up" on that whole metabolism thing--
Be prepared, it goes away, LOL.