Stop carrying weight on perineum. Put your weight on the pedals.
Go for a ride with no saddle. Main problem with that is saddle is part of steering. So be careful. Just getting down the road with no saddle should be no problem.
Stand on the pedals. Stand a lot. Standing gives instant perineal relief. Sitting on the saddle should be 99.9% as good as standing.
Six hours with a fitter? Doing the same thing over and over again expecting a different result? Forget this fitter. Forget fitters in general.
Everyone has a perineum. They are vulnerable. We are all at risk of having the problem you have. Most of us succeed in riding the bike.