I know how you're feeling, i've gone through similar situations. I've never had a relationship due to my sa. I've had women over the years show an interest in me, and they have tried to get to know me, but i've pushed them away because I was too nervous to get close to them. At the same time that i'm too nervous to get involved with anyone, I am also so lonely not being in a relationship. It really sucks, doesn't it?
I've also done the hiding away thing as well. When I lived with my parents, if anyone (even relatives) came to visit, I would hide in my bedroom and try to be as quiet as possible. What was most embarrassing was that my mum would let them know I was upstairs, so when they would be going they would shout goodbye to me, which made me feel really stupid for hiding away. I've also hidden and pretended not to be in when people have come to the door. Earlier this year someone kept knocking the door and ringing the doorbell for ages, and I just hid out in the kitchen. Just when I thought they had gone they came back and started knocking again so I hid again. I still don't know who it was. I try not to do this now, however hard it is for me, I now try to answer the phone and the door. The anxiety of seeing someone has to be better than feeling ridiculous for hiding away.
Its great that you've joined these forums. You'll find it a great help to discuss what you are going through with people who really do understand. I know it has helped me immensely since I joined two months ago.