Why do you have to find another group of friends, if you like someone. It should be a compliment.
You cannot control smiling, but maybe if you smile more often -it wouldn't be so obvious if it is someone you like. However, it's true -stifling emotions, find a way to come out in other ways, such as resentment. That is your subconcious at work.

Seriously, it could get embarrasing if they don't feel the same- but it shouldn't be the end of the world. Also, could you not look outside your circle of friends to find someone who you could be into, externally?