Being introvert = mentally ill?

Finally there's this serious matter that came across my mind about myself. Am I born to be an introvert or was I forced by myself to be an introvert? I've always thought that I fully understand myself, but it seems like that's not the case now.

After six weeks in the new environment, I think I still haven't talk more than 100 sentences, be it short or long. Let alone making (true) friends. I envied those who said that they made dozens of friends in just 3 days. To me, to be able to make 5 friends in a year is already a great achievement. Other than classes, I would spend 99% of my time alone at either the cafeteria or the library. That's what made myself felt very different from the others, that I deserved to be isolated. And then I started to relate myself with all kinds of mental illness because I've yet to see other people as pathetic as me. It was painful.

I was always told that time will change everything. Yes it did. But for me it's more to a destructive change rather than a constructive one. The only place I can talk well in is the Internet. But then my mom said that my addiction towards computer is the cause of my present state. That made me even more miserable.

Recently I Googled about introversion to find if it's really a kind of mental illness or something. I was given informations that introversion is just a kind of personality. For mental illness, that would be autism, but I know I'm not that kind of person that locks myself in my room and won't face or talk to everyone. I'm just an introvert among many other introverts that I haven't met before that lives in an extroverted world. Instead of changing my personality, I could adapt to this world slowly. No point changing myself to lose my own self, for now.

Although introverts are usually misunderstood, we tend to make less friends when we don't reply much to others when they talk to us. When I say don't know, I mean it, not because I'm too kiasu to teach. Humans are social animals regardless of their personality, and everyone would like to have some friends as their companion. It's just that the way introverts make and define friends differently from extroverts. Just because introverts have their own set of rules, they should not always be labelled differently. Being introverted has its advantages too, though it differs with each individual:

10) Work Well With Others, Especially In One-to-One Relationships
9) Maintain Long-Term Friendships
8) Flexible
7) Independent
6) Strong Ability To Concentrate
5) Self-Reflective
4) Responsible
3) Creative, Out-of-the-Box thinking
2) Analytical Skills That Integrate Complexity
1) Studious and Smart

Source: http://www.lifehack.org/articles/lifehack/top-10-advantages-of-introvert.html

For any other introverts out there (I just know there aren't any introverts here because I know who are my readers), visit these extra links and you might find it useful. Extroverts ignore these unless you would like to know more about introverts.
The Introvert's Personality Traits
What Introversion is NOT

So, don't worry, be happy. I shouldn't be worrying about my introverted problem now, but my 3 tests starting tomorrow. Holy cow I picked the wrongest time to do these. Bloody hell.

(A somehow hanging post, because I was interrupted by my sleep yesterday night. It was supposed to be posted yesterday, now my thoughts got lost.)