Struggling with my partner's NRE

Hi, I'm new to this community and fairly new to polyamory. My boyfriend (27m) and I (26f) have been together for over 5 years and we've been poly for the last 1,5 years. I haven't dated anyone else because I don't have enough resources right now, but my boyfriend has dated actively the whole time. He met a girl about a year ago, they started dating quite actively and they've been together for 2 months now. The whole time he's been mesmerised by her, he talks about her a a lot and he fell for her almost immediately after meeting her. She's really great and I like her too, we spend a lot of time together all three of us. The arrangement is something like a kitchen table polyamory. My relationship with her isn't fully platonic, but I don't see myself falling for her.

He obviously has NRE, I struggle with it and we've talked about it a lot. Our communication is excellent. He doesn't want hierarchy in relationships, I sort of do and maybe that's the root issue here. I'm jealous, I feel quite insecure, unappreciated and insufficient. I'm not really jealous of her, I really like that she's in our lives, I'm jealous of the way he treats her. What bothers me the most is that I feel like I'm his mother (we live together, with two roommates) and she's his girlfriend. I take care of him, our house, all of our affairs, I clean, I cook, I make sure the bills are paid, I help him finish his degree and make sure that his courses get done, I do everything from changing the sheets to booking his appointments, like a mother of a young child does.

MOST OF THAT IS FINE FOR ME because I am a very motherly person, I enjoy cooking and cleaning and doing those 'trad wife' chores. It gets frustrating sometimes but we're finding our rhythm in that department, we've talked about this too. What bothers me is that now that we live together (I moved in 2 months ago), our relationship is very much just talking about groceries, house chores and the girlfriend.

I feel unappreciated, because all of his romantic efforts got towards The New Relationship. We don't even have sex, because he's never in the mood or doesn't have the time or whatever, but I know he has a lot of sex with the other girl. I've gained a lot of weight and I feel insecure about my looks so this makes me feel really unwanted and tbh, ugly. She's smaller than me and he frequently talks about how cute and small she is.

This rant makes him sound like a bad boyfriend, but he really is a good partner. I think I just have so many little irritating things in my life right now that the end result is this. Like I said, we've talked a lot about this, we talk about our relationship every day. I'm feeling a little defeated because this situation has been going on for so long and I don't really know what to try next in order to feel better. I'm tired of bringing this up with him because NRE is a natural and a very nice thing and I don't want him to feel bad about spending time with his new girlfriend. I also don't want to guilt him into be more romantic towards me or to gave sex with me.

I almost wish that he would say that he finds me unattractive so that I'd have a 'proper' reason to feel bad :D How twisted is that? Anyway I tend to overthink everything so I'm just hoping to get some new perspectives here before I do something immature and petty out of frustration.

EDIT: Thank you for all the replies I got! This has helped me a lot. I realise this is all very complicated and I'm looking to start therapy once I have the money for that. The replies in this post made me realise that it's my own responsibility to set boundaries and voice my thoughts and desires and I can't keep hoping it'll all change on its own. My partner is currently staying over at his other girlfriend's so this is the perfect time for me to think about the replies I got. I will write down my thoughts, show them to him and I'll probably show him this thread as well.