Nginx infinite redirect loop
Solution 1:
I think you probably have Wordpress configured without the 'www' subdomain in it's URLs, and this is conflicting with the way you have Nginx configured (with server_name www.compassionpit.com).
So, when you visit compassionpit.com/blog/ Nginx redirects you to www.compassionpit.com/blog/, this request then hits Wordpress which redirects you back to the bare domain compassionpit.com/blog/.