I Always Get Asked Why Im So Quiet

I am socially awkward, I don't know how to talk to people a lot, and sometimes I even have trouble keeping a conversation going. Other times, it is because I have so much on my mind. It is easier to give a short response than break down and actually pour my heart out.

Others just think I am in a bad mood; I'm not, I just don't smile a lot especially when I am reading. Some people seem to think I am annoyed when its just me concentrating.
Just naturally quiet I guess was brought up that way.