A Brooks is very sensitive to the overall fit of the bike as others have said. Small adjustments make a big difference. I fine tuned mine over the Winter while I had it on a trainer. I found that I had my seat too high causing me pain in the taintal region. I also made sure the seat was positioned properly for me as far as setback and angle was concerned. Mine is very slightly tilted up. I road outside today and it felt absolutely amazing. I was also wearing Levis. My seat has around 900 miles on it now and feels great.

Check your seat height as someone else mentioned. I was shocked at how much too high I actually was. I was rocking and didn't realize it.