First of all - no matter how you position your weight in the saddle, it is all still going to be on the horse's back. Leaning forward, back, sideways, etc doesn't fly in dressage. And if you actually think about it, sitting in the tack and dispersing your weight over your seat in balance instead of just your stirrup bars is going to distribute your weight over a greater area, therefore creating fewer pressure points.
And I'd like to point out that your attire wouldn't work in dressage either.
But overall, looking a the work you and your horse are doing I would say that a switch to dressage wouldn't be a bad thing.
And in a quick google search of "dressage in York, PA" yeilded half a dozen barns that claim to do dressage. I'm sure there is one good coach in your area. My coach lives a 4 hr drive from me :P