I was diagnosed with Social Anxiety Disorder and from what I've read, Avoidant Personality Disorder seems like an extreme and persistent version of it (Somebody may be able to correct me there though). I sort of self diagnosed with AvPD but nobody ever applied that label to me.

I'd really recommend trying to get yourself some CBT as this helped me. I wish I'd sought it out at a younger age. It works by challenging your thought processes and gradually getting you to experiment with changing behaviours and gradually doing things you've been avoiding.

I managed to get some group CBT last year which was really scary but helped. Before that, my doctor recommended some online courses - one based in Australia called MoodGym. I never really finished the online course and found face to face therapy better but it's a good start if you can't get any therapy straight away.