Higgins I've been going through exactly the same thing, I'm currently living in Liverpool at the moment, might be a link there? [/bad joke]
I suggest just take a break from thinking about it, thats what I'm trying to do. If you can take a vacation then go for it. I'm afraid what you describe is one of the signs of Depression.
Try something new, like painting, or modeling with clay etc. Do something physical instead of building something on the computer.
As part of the engineering course I'm on, We had to use this new Lego NXT robotics thing. As stupid as it may sound when using it, it made me really happy, because its something physical to build and create.
Thats what you should do, with either some modeling clay or just whip out a bit of paper and a pencil and just doodle freestyle.
It will make you feel better, as well as gain some better artistic skills.
Hope that helps.