"Just Be Yourself."

So every time I go into some sort of new social situation I am told to "be myself." But as cliche as this sounds, I'm not quite sure who that is at this point in time. I feel like I've always put up fronts with people. Not something completely fake and ridiculous, but I just edit my behaviors depending on who I'm around.
When I'm with my AP Gov and Debate friends I always try to act smart. I laugh at their jokes even when they're not funny or I don't fully understand them. I always try to be witty and try to be knowledgeable even though it's probably evident that I'm not.
When I'm with my "athlete" friends, baseball and basketball are everything. We don't talk about anything else, and I act as if I'm fine with this.
With my drama friends I always make my actions a little bigger, my voice a little louder, and make myself stand out more.
With David and Texas is when I feel the most at ease, but I still cannot decide if that is "who I really am" or if I am just putting up a front with them as well.
It sounds super cheesy, but I'm not really sure at this point of who I am. What I do know is a couple of things that i'm not.
I'm not:
-religious
-stupid
-a stoner
-a political guru
-a performer/talented
-a singer/actor
-an athlete
-an emo
-a goth
-a prep
I don't fit into any of the stereotypes, which sometimes makes me wonder where I fit in at all. It's all extremely confusing.