If you ride English, wear full seat breeches and half chaps. Your saddle might not be the right one for you.
Do you ride more than once a weeK? If you ride quite infrequently, you can get sore more than riding more frequently , because over time you toughen up .
BTW, I am 54 also. I have been bruised by saddles that didn't fit right, but in my dressage saddle, I am never bruised. I ride about 3 times a week.
I am not thin, (by any stretch of the imagination), so maybe my padding helps in this regard?