When I had that issue is was because the saddle I was riding was too pear shaped (gilles berthoud aspin), once I switched back to more of a t shape the problem went away. As soon as my foot heals I am going to try a Selle An-Atomica but at the moment I am on a fizik vittesse sport (old one) some women hate them but it fits me perfectly. Am assuming you have looked at all the fantastic saddle posts? Have you measured sit bones?