Wierd habit

Strangely I have this wierd habit of always trying to smile, and laugh at lame jokes while in a conversation. I also try too hard to make other people smile or laugh. Hmm..... I have a co-worker who describes me as being bubbly, but really behind all my smiles is an emptiness that's sickening. I try to just be natural and not hide behind this happy facade, but it doesn't seem to work. When I'm with my family though, my facial muscles suddenly relax and I stop being so damn cheery. I wonder if I was like this before? Why the heck do I have this annoying habit? Is it because I want so desperately to please others and appear good natured?