Introducing BDSM to someone who may think it's wrong

I'm a sub woman and I want to introduce BDSM to my boyfriend. My friend thinks that my boyfriend has dominant tendencies but is suppressing them because he believes that it's abuse. I don't know if that's true but I do know that he is not being assertive in ways that I need him to be.

I tried to express to him what I'm into before and he agreed he would try it but I could tell he was very apprehensive, I don't think I brought it up in a way that was helpful. Nothing has changed since then. Maybe he is overwhelmed and doesn't know where to begin. I just hope it's not that he isn't into it but is willing to pretend for fear of losing me.

Is there any literature or videos or anything that introduce BDSM as an act of love? I want him to see that this is something that is wanted and desired and that it's not abusive.

Any help would be appreciated on how to get this started.