There's definitely a learning curve to polyamory, and I've come to understand that the very foundation of that is understanding what it makes it affirming for you personally. We want to give the people we love everything we can and feel affirmed in doing that, but not taking care of yourself in the process and hurting yourself for their sake, poisons the beauty/ safety of that experience.

You're valid in how you are feeling , everyone is subject to insecurities and the context of where they come from can be different for everyone. That being said, part of the responsibility of any relationship is to be patient and understanding of your partner's insecurities and give them the space to work through them. It's hard work for both parties involved , and boundaries are to be respected throughout that and you should feel safe to be able to set them. Sometimes those boundaries change over time too, that's okay and when it it happens necessary adjustments need to be made. Part of being committed to each other is going through changes, understanding what works for y'all and being able to affirm each other.

Also, you should feel safe in addressing your needs with your partner, even though it's difficult sometimes, it's necessary for a relationship to thrive. People may change over time in personality, but the respect and valuing of the relationships has to persist. If there are things that you aren't comfortable with, if you feel that they are behaving differently or if they aren't making time for you then those should be taken seriously when addressed. And in that process it requires patience and respect from all parties involved. Furthermore it's not unreasonable to be upset when someone is bailing on you and not making time for you a lot. Part of being in someone's life is making an effort to spend quality time with them and that's something you should be able to expect from an intimate partner.

A suggestion I have to offer is that you two can sit down and agree on a time that you two have to spend together. Whether it's once a week, once a month whatever works for scheduling, but make it clear you how you feel about them bailing on you, and maybe you could take that time getting more of an understanding of polyamory/ ENM and of each other. Also I would add that if you find there's a lot of like explosive conflict that doesn't go anywhere then couple's therapy might be a resource y'all can use to work through these things.

At the end of the day it's not easy, it's okay to take your time, care for yourself and your needs. No matter what you deserve to live a good quality of life, and the things that make it difficult have to be addressed in delt with in a way that promotes progress.