Don't see a chamois mentioned in the original post. Are you using a chamois/padded bike shorts/bibs? If you aren't, get some, if you are, maybe it's time to try a different brand, along with a different saddle. A friend, on the thin side, fought with saddles for a long time. He's ended up with a Selle Royal Respiro (don't know if it's the Athletic or Moderate, but says it works great for him. Of course, we all know how saddles are--some are great for one, end up in the trash for others.