Now she knows
After being married for 25 years and the kids grown, I admitted to my wife that I was a masochist. She told me that she knew and had known even before we married.
One of the things that I did most often was to clamp my nipples with locking pliers and keep tightening them down until I couldn't stand the pain anymore. I also would stick needles through my nipples and sometimes I even stapled them to pieces of wood. And on occasion I would burn them with a soldering iron.
After I told my wife, she said that she would help me. She now does all the things to me that I used to do to myself. And now I have pierced nipples with a chain between them that she likes to pull on.