An introvert gets refueled by being alone, though there tends to be a spectrum between extreme introvert and extreme extrovert. As I've gotten older, I've moved to the middle of that spectrum, often needing to re-charge by myself, often needing the company of others to re-charge. It's kind of weird. That being said, there's nothing wrong with you being an extreme introvert, but Stefano has a point. Your depression probably adds to your desire to be alone. It also probably adds a horrible irritability to the mix. It's possible, too, that you have either biological or psychological sensitivities to certain types of sensory input. Don't know. I would say keep those close friends close, give yourself space from your family without completely withdrawing, and challenge yourself on occasion to spend time with acquaintances or new people, maybe chatting for a few minutes with someone in a coffee shop while in line or something.

It's hard to tell where the line is between just being introverted and letting your depression push you into isolation, but it seems like a warning light has turned on in your head. Pay attention to that. Sometimes that's when I send out an email to a friend I haven't seen in awhile, just to make an easy connection.