You look really young,but you look fine and I don't think you should be bothered with trying to get others opinions about it.Also,people have different preferences of what they find attactive.So I wouldn't really listen to people saying grow out your hair,gain weight...whatever.Theyre saying what THEY think is attractive or would be attractive.So just be you,thats what I think.
You're good looking. You just look younger than your age. Which by the way isn't a bad thing because you'll age slower/better most likely. Don't worry about it. I get asked if I'm a freshman all of the time and it annoys me.