Trading Love for Sex?

Sometimes I wonder if my relationship with my dominant lover Z is really about trading love for sex.
I love Z, but I am not in love with him, and I have increasingly come to face the truth--what I most love about Z is our D/s relationship and how much the bird in a gilded cage/caught princess thing turns me on.

On some level, I think Z knows all this and part of his tactic with me is to fuck me into submission, to make me so satiated and enthralled that I'm content to continue the relationship.
In other words, he uses sex--the way he touches me, the way he controlls me, the attention he pays to me--as a way to get--and keep--my love.

But is it a fair exchange? And is it an exchange I want to continue to make?
On Z's side, the tradeoff is to keep his lover sexually and emotionally enthralled so he can have what he wants--a real, submissive girlfriend.
On my side, it feels like I'm agreeing to be the girlfriend--to act that role--because I want the sex.

I enjoy being submissive. I also enjoy having multiple relationships. I don't see how I could have an intense relationship with a dominant who would let me decide who else to be involved with.
So I feel like I want to have a couple of mutually exclusive things--an intense D/s relationship some of the time, and the freedom to see D (and occasionally others) other times. That just feels like something I am NOT going to get.

So which part do I really want the most? A Master who can control me love me dominate me or a boyfriend or two where any D/s is just a little play?

I don't know. That is why it is easier to submit to Z, to fall back into his world, but when I am apart from, in my own life, it just doesn't feel right.

I know I am trading one thing for another, not totally acting from the heart, and that bothers me. And yet...Z is such a wonderful dominant....this is difficult.