Out of practice socially?

The last few weeks I've been getting increasingly uncomfortable with the vibe I feel like I'm spreading. It's hard to explain, but it feels like the person I am when socializing is so different from how I really am, when I am alone, that people think I'm somebody completely different from who I really am. The way I construct my sentences, my laugh, my voice, my stance, my observations... They are things that are a part of me, sure, but they feel like they're part of my sinister, annoying side...
What the hell is this? I'm not trying to put on a mask, but it does seem to happen automatically somewhat. It's highly uncomfortable??_
I feel like I'm becoming more and more robotic??_ I have to highly evaluate everything I say, how I say it, what face I'm going to make??_ It doesn't seem to come very naturally. During a conversation I'm thinking like this ??Hm, which face should I do now, what's appropriate to say/do next?? etc..

Quit overthinking it and just be.

I'm not shy or anything, or worried about what other thinks. I mean more for my own sake. I feel like I can't express who I TRULY am inside. Nobody knows what I'm like. I think very much, so because I constantly have this speed of light thinking, I feel that everyone else is picking up this and know everything I think and feel inside. But they don't of course. To them I'm just a silent person. If I start talking about something I take interest in, they just look at me like I'm insane.