My teeth don't support my smile; thin lips only when smiling; short, narrow smile; what are my options? (Photo)

It's really hard for me to smile for a camera. When I'm laughing with friends I can smile, but when I'm asked to smile, I can't. It seems like my teeth give my lips no support, making things like talking properly and smiling really uncomfortable and hard to do. When smiling, my lips pull really tight across my teeth and flatten out. My lips are decently full at rest, but they almost disappear when I smile. My smile is very short and narrow because of my teeth. I have an overbite as well.