please look for the favorite saddle and hated saddle thrreads.
If you find a saddle that works for you it might take a week.. .but, if you're used to riding 5 miles at a time and you jump to 50, you're going to be sore
probably.
it's not that simple. But if all other parts of you are doing okay, you either need a different saddle (what is it?)
or you need to get it repositioned.
good luck