My smile looks small and oval shapped. Why is this?

Hello, My smile, or the look of my smile looks small and oval shapped, it's a bit difficult for me to smile, I mean it feels like I need to stretch my face harder in order to smile and show teeth. I've attached an image of me smiling, this is the maximum I can do to show as much teeth as possible. Something wrong with it, it's not wide and looks weird. I've attached another image of a smile from the internet that looks more relaxed which is something I can't do myself.