You say it's confusing, and it is. Everybody is different.
My boyfriend likes the fact that my secondary loves me, and that I love him. He would hate the idea that it was just about the sex.
Speaking for myself, I could deal with my bf having sex with another, but it would kill me if he loved someone else, I would suffer from emotional jealousy. It does not bother me at all that my secondary loves his wife, and I dont think I would care if he loved another woman as well as us. Maybe it just shows that I love my bf more than my secondary, and that's why I dont want to share him.
My bf also hated me coming back to him marked up. For him sex is directly linked to the love that we have and he does not like BDSM at all, it turns him off to think of me liking, and allowing myself to be dominated or spanked. I do like it though, and he would not ask me to stop doing it. I also now make the effort to avoid going back to him with marks. Scott has stopped using a particular paddle which bruised my ass, and makes sure the restraints aren't to tight. I love being a sub to my dom, but I dont want to upset my man because of it, so I compromise.