Okay, what you've described here isn't D/s. It's more M/s. Now, don't misunderstand me - you've made it clear she's the initiator in this relationship change - she's completely willing to be his slave. You even use that verbiage several times, showing she is not just his submissive.
You also delve into a bit of autoerotic asphyxia there at the end. I admit to not being prepared for that - strangulation during intercourse is not something that appeals to me.
I know this piece is older, and perhaps you've learned a great deal more about the lifestyle since having posted this. Unfortunately, I've no way to know if that is the case, so I am going to direct you to a discussion in the forums here regarding D/s versus M/s:
http://www2.adultfanfiction.net/forum/index.php/topic/48221-slave-versus-submissive/
You're certainly more than welcome to chime in on the discussion there. I have to admit though that I'm very concerned if this snippet does represent your understanding of the lifestyle.