I have evolved (or devolved on how you look at it) from being an introvert to just straight up asocial; as everyone else has described, this is not healthy at all. I used to not be this way -- I used to look forward to hanging out with people, but now it just drains me and is a chore. I feel like I'm an actor: "All the world is a stage and we are merely players". Everyone has their own traits, and I'm pretty sure you can't change your social desires at the end of the day, but you can of course always force yourself to leave the house.
I have never stayed in my room for even a day, but if you gave me a week off work I would have no problem with just staying home, and I would have no desire to leave (blame technology).
When I graduated high school, while all my friends were having grad parties, I just sat in my room reading the Bible, watching the Atheist Experience and trying to figure out why I even exist... all that thinking got me nowhere, but I guess we all have to go through our phases.
I also went through my "nothing is real" phase when I got out of high school... totally not healthy, but for me it was unavoidable.
I have literally gotten so far inside my head that I don't think I will ever get out. I feel like I went on acid trip or something, but have never touched a drug in my life.
Edit: This is why I love Todd Rundgren... what other artist puts out a ballad about existential crisis after having a top 5 pop hit?
Sometimes I just feel so afraid
But I know that no one else has it made
So if I just believe in myself
I won't need no help from nobody else and I can make it alone
Rock for the skull... not exactly the type of thing you would play at parties.