When I talk to others I notice I have a bad habit of always smiling really big, looking down, or away at the same time.

I do this because I don't want people to think I'm rude & I don't want them to feel uncomfortable if I stand there like a stoic. I even fake laugh (yeah I cringed typing that)

Question is, what do girls think of guys that don't smile like a horse all the time? Am I a douche if I don't smile when somebody tells a joke and they start laughing? Will people distance themselves from me if I stop my habit?