I’ve been there! If its not your body position, and mine wasnt, its your saddle. I had a LOVELY keiffer i used that seemed to fit practically everything, it put me in a WONDERFUL effortless position, and thoroughly rubbed me raw until i bled… I put up with this for a year thinking it just must be me, i never heard others complain… But eventually, i gave myself a UTI from it and had to start looking into other options. (And no, i do NOT ride on the front of my crotch, this was from rubbing and bleeding around the middle area!
I tried saddle after saddle. I even gave up and used a Bob Marshall Treeless western saddle which was like sitting on a pillow and rubbed not one bit! It was very bittersweet selling it when the time came!
But i did eventually find a saddle that worked and have sat in a few others that work for me now that i know more of what works for my body.
I had to kiss a narrow twist goodbye. No matter how much i may like it for my leg, it did not work in the sensitive area… I do not do well with wide twists, but a good medium twist with a seat that flairs out to hit my seat bones well works very nicely. If your seat bones are “falling” off the seat around the saddle, its putting more pressure on the center of your crotch… YOUCH.
I have a wow that i love that fits one of my ponies perfect, but not the other. I am presently trying treeless for the other one, i had a brand not available in the US shipped to me, but of course they sent me the wrong size, so i’m now waiting for the right one to come back… But as for comfort in that area, (and this is sitting in a 16" not a 17" i normally ride in) it was VERY soft and comfortable. I do not know if all treeless saddles ride like this one, but for comfort in that area, i was thrilled. So perhaps treeless may be an option for you if it works for the horse.
But basically, sitting a trot or a big moving canter in a narrow twist anything will murder you. I think some of us women are just prone to be much more sensitive in that area and this issue effects other activities outside of riding too! For those women, try a more “medium” twist or if your body conformation can swing it, go with a wider twist, something that will not “ride up” into your crotch. I have found different underwear made no difference, riding with a pad made it MUCH worse, more padding is not the answer, its just more to push up there and hurt you. However, heaven forbid you try to ride for any length of time in a tampon, that about kills me, so then, i have to wear a pad and do different things that day, do some two point work, or double post to work on my leg position and balance, things that do not require a more deep seat.
Hope that helps. If its not your body position (and yes, it very well could be) then i would look at the saddle! You are not alone! But there are “happier” options available! 
