I used to ride my mtn bike without padded shorts and never had a prob. With my tri bike I still have tenderness after long rides. I had to change my seat 3 times to find one that worked for me. At my LBS, they let me try a saddle, then return it for another within a few days if it didn't work. I did that until I found one that works. I'm riding the Terry butterfly. Works for me. After really long rides, it's still tender- but that goes with the territory of really long rides and being down in my aeros for long periods.

Keep trying diff. saddles until you find one that works for you. We're all anatomically different, so find one that you can live with!