Polyamorous relationship with relationship trauma advice please.

My boyfriend and I have been together for 2 years in July. I’ve always had polyamorous relationships with my previous partners. I don’t think humans are inherently built for monogamy, that it’s usually an active choice. (With exceptions of course) In every past relationship, the “if you give a mouse a cookie” thing happened. I trusted too much. I gave them too much leeway. And they all broke the boundaries I had set forth. If you don’t know, that’s how you cheat in a polyamorous relationship. You break boundaries with the other person/people.

My last ex was the worst partner I’ve ever had. She cheated, made fun of me for being fat, told me when someone was better at sex than me, etc. not to mention the physical, emotional, and sexual abuse. It was awful.

I never had time to process everything from that relationship. My grandmother died right at the end (that’s what made me leave. She got mad at me for wanting to stay with my grandfather for awhile to help him out) of the relationship, and obviously that’s more important.

My current relationship has been great! I love him, he makes me feel safe, he helps with all of my various traumas and is genuinely the best person I’ve ever met. He recently decided to start with the polyamory. But I have a few issues.

1. he didn’t tell me when he started looking for other people
2. he didn’t tell me when he found a guy he wanted to date (we are both bisexual.)
3. Sometimes he forgets when I ask to have special time just between the two of us without messaging his new friend.
4. something to keep in mind as I continue is that he has known him online for a month and a half and met him in person a week and a day ago.
5. he lies about going to bed and calls him for hours, instead of spending time with me like he promised.

I asked him yesterday if we could pause and he could be friends with the guy for awhile because I didn’t know how bad it was all going to affect me. I didn’t realize I hadn’t processed my last relationship, and I didn’t realize how traumatic and anxious and honestly horrible this situation would cause me to feel.

At the beginning of our relationship he told me a lot that if I ever wanted to close everything down that would be fine and he would never choose someone else over me.

He did yesterday. He said if I needed the break from polyamory he was just going to need to pause with me instead. He chose this person he’s known for a month and a half (just met irl last WEEK) over me. He’s on a date with him right now and I’m extremely uncomfortable and anxious and I want to cry. I don’t know what to do.