Everyone else has had good suggestions. Just a couple of things to add -

Chamois is supposed to line your inner thighs as well as your seating area. If it didn't, you'd have seams where your thighs meet your perineal area, and everyone would have the trouble you're having.

Has "every pair of shorts you've tried on" had a very bulky chamois? Even though it seems most women are more comfortable in minimal chamois, for some reason few LBS stock them. You might try to find shorts with thin chamois - spinning shorts and triathlon shorts tend to also have very short legs, which aren't for everyone, but also very thin chamois. There are a few true "road" shorts out there with thin chamois, including my faves, Castelli Provocante (kinda short for my taste), Castelli Vizio Due, and Etxe Ondo Very Short (which are not very short ).