I had a huge change of topic because i got so badly sick of what i was doing, so i kind of know the feeling. I even switched from maths to computing because i was so fed up with the whole thing. Are you writing as you go? Don't just let yourself get burnt out from doing too much thinking and experimenting -- you have to write to organise your thoughts. I don't have a gf either because it just doesn't suit me, although i asked someone out not long back -- i think she is still sort of thinking about it. In a way I'm not too sure either, see how those things go. Take a holiday and make sure you write some stuff, i find it clears the head.