Paul, looking at your supplied Google analytics, it seems that Google has dropped you.

They may have removed you from their index.

I suggest, if you have not done so already, that you use Google’s webmaster tools. Add your site. Ask Matt Cutts for his assistance (on his blog).

It could be that Google’s algorithm has decided that your site is bad and just dropped you.

Another way for you to get traffic is to start using your stumbleupon account. SU gives me MORE traffic now than Google. Bonus is that I get local traffic from it, whereas Google sends more internationals than locals.