The man I thought was my soulmate broke my heart

We met back in October 2021. I (f28)asked him (m32) to go to a scary movie drive in marathon. We spent the entire time talking. Literally all night. We didn’t leave the drive in til 8 the next morning and like 95% of that night was *just* talking. Talking about our pasts, talking about our hopes for the future, what we hoped to find in a partner. We vibed so well. We spent that entire weekend together and I knew I was in love by the time it was over. I’d never felt anything close to what I felt for him.
I felt like I’d been waiting to meet this person my entire life. I hadn’t gone on the date with that intention. I hadn’t even considered it. But I felt like I’d found my soul mate.
Things weren’t always completely smooth sailing between us. We actually live 4 hours apart and he has to travel a lot for work. But, I felt so connected to him I was willing to make it work.
A few months in he told me he wanted to be polyamorous. I balked because my last serious relationship (which was also my first, and ended up being abusive) my partner demanded polyamory after I’d caught him cheating on me basically every time he had an opportunity and he wanted to be able to do that without getting “in trouble” anymore.
I told m32 everything about that. I said I wasn’t sure I could do that, but that I’d try to trust him and give it a chance as long as he was honest and forthcoming with me if he took another partner.
After a good while, I kept seeing another woman, S, comment on his social media being super flirty. I told him it made me uncomfortable and asked if there was anything between them. He told me they’d fooled around in the past but that poly stuff was a deal breaker for her and no poly was a deal breaker for him.
I tried to let it go. I really did. I tried to believe him. I told myself he wasn’t the one who caused my trauma and he deserved my trust. But it just kept happening and they kept getting more and more flirty to the point where she’d made some comment about sending nudes and talking about loving him.
Every time she’d say something that I felt crossed a line I’d go to him. He’d assure me i didn’t need to worry, but every time I felt less and less assuaged. He never again said they weren’t together but he never said they were.
Two weeks ago he texted me, telling me he needed to tell me something and that he was hurting badly. Of course, being worried, I asked what was wrong. After much prodding he finally tells me that S was pregnant with his baby and just had a miscarriage.
I am so fucking devastated. All my trauma came rushing back to me. He’d talked so many times about having kids with me. Hearing him talk about his “dreams dying” with her baby broke my heart. When I asked him why he hadn’t told me they were seeing each other he said his ex had given him trauma about it.
I’m just so hurt. He lied. He put his wants before my needs. Would he have ever told me if she’d had the baby? How TF was he planning on making that work? I don’t even feel right chewing him out for lying because he’s grieving.

I wouldn’t wish the death of a child in anyone and I see it as an absolute tragedy, but I’m also grieving the trust I had in this man.

Tl;Dr my bf cheated on me and I only found it because his side chick had a miscarriage