If you are paying 600 to commute and 300 rent, I am sure you would get a much better deal closer to your work. For 900 you could live very well in London! But I know it is possible to get decent rooms in a flatshare from around 400-500 pcm, and this would actually enable you to save some money!
Try look at spareroom.com
Take your time to view places, see that you like your potential flatmates and think you can bond with them, or at least live in peace with them!
Make a profile on spareroom, chose a decent picture which shows your face, with a smile, perhaps taken in a good location.
Take care how you present yourself. Like for example, if you say "Hi, I am Brenda, I work in Marketing/nursing/bookshop, and looking to find a new flatshare near my work place in WC1. I am quiet and easygoing, tidy and like to read or go to the cinema in my spare time" you will probably get interest from quiet and likeminded people.
Equally, a "Hi, I am Brenda, love a good party and want to find sociable flatmates to hang out with, love some wine of an evening, and love to explore all that London has to offer" you will probably appeal to some party animals!
Think about the sort of people you would like to live with, especially if you have some anxiety issues. Loud and cheerful people who like to party, or quiet people like yourself?
I definitely think you should move out. Living like you do now does not sound as if it is doing you any good, and with a terrible and draining commute!