Oh, dear. I wish I could help you feel better. I will say one thing, though. The last thing you said, about fanfiction? Isn't that sort of the point of reading and writing? It's an escape from the harsh reality. I don't know about you but reading makes me feel better. Maybe there's something for you to read, to help you cope with your difficult (read: bitchy) mother?
I experience social anxiety as well, but so far I haven't found a way to make it better besides just forcing myself into things. And that's not fun. I really wish I could give you better words of advice or comfort.
I hope it gets better.