@OP; I used to be, and in fact still am just like you; I was afraid to answer the doorbell or the phone, I never used to ask questions in shops and in college I rarely ever asked questions, let alone make a point in a discussion because I was afraid, for no real reason, my parents have always assumed I am just shy, and I doubt they or in fact many other people understand exactly how I feel.
What did help me hugely, was going to Uni. Before I left I never used to be able ot make appointments, and eventrivial meeting such as with my tutor used to cause me worry and make me very nervous (sweating, racing heart and shaking), I never used to make comments in lessons because I was too scared to put my hand up. Getting essentially dumped in a strange place with no one I knew was the single most scary event of my life, in fact my parents didn't think I'd last two weeks, and neither did I.
I'll admit certain events through my life assist in the way I think I am today, I will be the first to admit I am very shy, I am the type of person who sits in a corner on his own or with one or two friends at a party simply because the fear of meeting new people is too great, some may say this is stupid,
I started to learn that i could talk to strangers, admittedly it's not something I enjoy I still get very nervous, my hands shake and i am so worried about saying the right thing at the right time i end up nodding just saying yes or no and so on. I am still incredibly indecisive and I constantly worry about how I come across to people or should i have said this or done that, but I have started to learn that what ever happens it will happen and if I worry about ti it will probably be worse! That helped me a little but t still get worried about meetings with poeple I am aquitened with such as my tutor, but I have learnt to answer the door so things have improved!
Personally I don't think you are weird, being introvert and a 'worrier' is nothing to be overly worried about, would will I hope find that you have no choice but to talk to strangers and eventually you will overcome your fear, or at least not let it overcome you. You have realised this is having an impact on your life which is the first step, things will progress and get better, you wil have no choice other than to encounter strangers be it in social, employment or academic situations but your confidence will grow, just don't let your fears ruin your life.
As for the future, it is something that worries most people, some more than others when I was 18 (God that makes me sound old) I was looking at some very big changes, now I am 20 I am looking at some even bigger changes and they do still wory me I can tell you!
Anyway that was probably complete drivel and made no sense what=so-ever but maybe you'll realise your aren't the only person who feels like this!