What has caused me to change so drastically in life?

That's not unheard of.It is normal for some one who is shy and self conscious to out grow it once they reach adulthood.I was very shy and pessimistic when young.But once I turned about 21 things really began to change for me.I became more out going and had tons of friends.I don't think I stayed home one night from the time I was 21 till I was around 26.This is really something very normal for a lot of people.Just be happy and enjoy it.