It sounds like your partner has a case of the NRE's -- multiple cases, as he seems to be dating multiple other women. You are feeling jealous because he isn't treating you decently. He's doing things for the other women that he wouldn't do for you. What needs to happen here is that he needs to start acting better. He needs to start planning special dates with you. He needs to start buying you thoughtful gifts. These are things he should have been doing the whole time.
Do you do things for your long-term partner, like planning special dates and buying thoughtful gifts? Did you do that earlier in your relationship? Do you do it as much now, or less?
Some men never really do much as far as planning "special" dates, cooking, even buying flowers. Or, maybe they'll do it for a brief period at the beginning of a relationship. That's called courting or wooing, to use old-fashioned terms. Once the woman is hooked, those kinds of things become her job. The man just shows up.
We can't force our partner to change. If the guy here never, or only briefly, did those things, we can guarantee he'll only briefly do those things for the newer dating partners, too. At least there's that.
Generally I seek partners who are not "romantic" just during NRE, but continue to be thoughtful, and give an occasional gift ("just because," as well as on birthdays and xmas), are invested in cooking, cleaning, household chores, deep cleaning, yard work. If they aren't good at planning special dates or getaways, when I suggest ideas, at least they need to be enthusiastic about helping me plan them and do them!
If they aren't this kind of person, I break up with them, or at least downscale my expectations. I go on to seek others who suit me more. I am patient and I don't "settle" for less than I need and deserve.
Reading up on the Five Love Languages can help. You can't expect to feel satisfied if your lover ignores your love languages.
However, I agree this is a "case of the NRE's." Also, for some reason, this couple was living together, but have now moved apart. Maybe the guy feels more like a bachelor again. He probably shouldn't be telling OP that he's cooking, buying gifts, and planning special dates for others. That's TMI.
If OP wants to plan special dates, she can. If she'd like more gifts, she can say so. If she wants him to cook for her, she can request it. However, he can refuse to do these things. And if that's a dealbreaker, if she feels taken for granted. she can break up with him.
Generally it is highly recommended in polyamory to NOT neglect your long-term partner when you're in the throes of NRE with another. Polyamory means many loves. It doesn't mean replace the old love with the new love. But if you fall out of love with someone when you catch feels for someone else, you are either not poly, or you are just no longer compatible with the prior partner.
In any relationship, mono or poly, time passes, and there's a real danger of taking our longer-term partner(s) for granted. It's a newbie poly mistake to devote all your energy and excitement to the new and shiny untried partner. Working hard to get them in bed can feel very compelling. But no one should thereby neglect the prior partners, or spend dates with the longer-term partner(s) just gushing about how excited we are with the new person, what we do with them, how often we bang, or the anxieties we have about them. (Anxiety about the new partner is part of NRE, "Does she like me too? Will she text me back soon enough? Did I act like a fool the last time I saw her?" etc.)
I suggest shifting your focus from what he does for the other women, to what he does (and should do) for you. That's where the root of the problem lies. You have every right to feel jealous when he's doing wrong by you.
It sounds like you have already approached your partner about how he treats you -- and he just plain doesn't get it. Or does he get it, but just doesn't care? Is he even trying to get it? You may find yourself in a situation where, whatever his reasons, he just isn't going to treat you right, no matter what. If you at some point find yourself in that situation, will you take any action on your end? What action will you take? You can't choose his actions for him, you can only choose your own actions.
