I Act Older Than My Age

I'm currently 21 years old and I have been told by my peers that I act like an old person, LOL. Ever since I was little, someone always pointed out that I acted much, much older than my age. Doesn't really help that unlike most people my age, I'm not interested in drinking, partying, or clubbing. I prefer going to bookstores or Museums and talk about history withs someone :)