He actually has decided he is going to slow down so much that, until I have had a few poly experience I'm comfortable in and am enjoying, that he won't be pursuing anyone (and although I have never asked him to do this, he still feels like he's doing it 'for my benefit', which I'm a bit afraid will make resentment happen down the line). I guess I'm just confused and scared. Confused because some days he says that what he might want is live-in 24/7 D/s like he used to have, and he knows I don't have any desires for that again, so he'd have to release me in order to pursue that, and some days he says he might try poly and it not work out and him be content with one relationship (incidentally, he does say he's happy with just me, he just knows he could be happier with other people involved, so that's what he wants)...but then he tells me that I'm hearing him wrong, and that the only thing he really wants has never changed since his second slave left, which is to have me as a live-in primary relationship leading to marriage, and to then have tertiary or secondary relationships with other female submissives in a non-d/s context. He likes variety. He wants to be sexual with other people. He wants to care about other people, but have the flexibility to see them twice a week or twice a month without hurt feelings because him and his other partner are secure and happy in their lives already.
Me? I don't know what I want anymore. Monogamy seems simple and happy. Poly seems complex and full of woe. But I don't want to close myself off to the possibility that someone wonderful could walk into my life and enrich it in ways I don't even know about yet. So I think I'm just scared of being replaced (even though he assures me I won't be), scared of being dismissed because I'm occasionally miserable (I have clinical depression. It often causes me to see the worst in situations instead of the best), and scared because I feel like I can't talk to him about it anymore--he just gets frustrated and hurt, and so do I. So I don't really have anyone TO talk to about it.
Thank you for the response. He really is being understanding, but I feel like a horrible person every time I get jealous or scared or insecure. I don't want to ruin this relationship based on insecurities, fears, or my being uncomfortable with feeling like I'm not "enough" (a fallacy in thinking, I know. Love is infinite, not a resource that disappears; just because we may both have jobs now that dictate totally separate schedules and thus not much time for each other doesn't mean we love each other any less, for example). I want to love him and be generous in the way he deserves, and open my heart to new experiences, and not feel like I misrepresented myself or lied to him when I started this relationship (he says I've changed and become more mono in my thinking, and that I don't think poly is worth the trouble). I guess I just got content and happy with the way things were when we weren't seeing anyone and working on our own relationship, and maybe I'm just afraid of change.