I am sorry you struggle.
The fact is that (GF) wasn't really willing to be in a poly relationship - she wanted me all to herself.
So GF was no longer willing to participate in a poly thing.
so she started treating me poorly and pushing me away.
That's not necessary. It's also disrespectful. It ok to try something and find out it isn't you cup of tea. But one could say something like...
"I tried this out. I thought I could. Turns out I cannot. So I need to bow out. If you are every available again for 1:1 relating, let me know. I just cannot be doing a poly thing."
.... instead of treating you bad.
You do not deserve to be treated poorly.
So it I know it had to end. But now I find myself in a very surprising and uncomfortable position: I feel resentful of my wife for being the reason I lost my girlfriend.
Your wife existing is not a reason why your GF doesn't want to poly any more.
GF just doesn't want to poly any more.
You may have to decide at some point if you prefer to stay with wife, or end it with wife and see if GF is up for a 1:1 thing.
But I suggest you DO NOT make rash decisions while still reeling from being treated badly and from the recent break up. Mourn and make peace with all that first, THEN decide what to do next.
If you are used to having your wife around to comfort you when things in Life go wrong, I get that you feel a bit lost right now when that comfort isn't "automatically" happening.
Wife is not at full strength right now. She already broke up with GF earlier. That's her ex too and she's still in a mourning process too. So check your expectations of her and of yourself.
What makes it worse is that I can't really talk to my wife about it or even show any signs that I'm sad about it because she feels hurt by it when I do - largely because she's still so hurt by how her relationship with the girlfriend ended.
You can tell her you feel sad. What's stopping you?
Just don't TMI the details. Something like "Hey, I feel sad today. I could use a hug. Could you be willing to give me one? "
It's just hard because right now I feel like she's rejecting me because I'm hurt over the girlfriend at a point where I really need her to be there for me. But I also understand she really can't be.
Have you asked her straight up?
"I feel X. I need Y. Could you be willing to do that? Or something similar? I know you are hurting also. Is there anything I could be doing for you? I think we need to be extra kind to each other right now."
You can see your wife is not in her best shape after a break up. So if you have to spell it out... spell it out. ASK for what you need from her. Remind her to do same -- that you are also around for her. Neither of you can be mind readers.
Don't become "hurting hermits" that turn away from each other in favor of cuddling with the hurt.
It's ok not to want to express to much of it to each other because you dated the same GF. (Maybe in future you decide NOT to "share" GFs because it leads to this weird place for you guys should things go wrong. )
But DO find ways to express the hurt so you feel better. Maybe talk more here, talk to a real life friend, seek a counselor, a poly meetup support group, etc.
I'm sorry it is so fresh right now. I hope in time you start to feel better.
Galagirl