Have you ridden tours on your bike with the current saddle and your current pair of bibs?

It sounds like your skin might be getting chafed. Sweating a lot can make the problem worse. Shorts that feel fine in cooler weather can cause irritation when you get very sweaty. You might want to try some chamois butter. And wash or shower right after you finish your ride, get out of your sweaty shorts as soon as you can.