Wit may be the wrong saddle shape. regardless if what saddle you choose you have to keep in mind that you really don't ride to much. so your butt doesn't really get used to that feeling. Going back to the shape if your saddle, ur your saddle is to narrow for. you and your sit bones are hanging off the edges than it can be very painful.
I'm not trying to be a salesman, but I had the EXACT same issues you were having. After much research I our based a cobb saddle from Cobbcycling.com I got the V flow plus and after four 50+ rides I couldn't be happier! it has a 6 month comfort guarantee so you don't have anything to loose.

http://www.bikeforums.net/showthread...r-to-sore-bums