My polygroup dumped me - like they're all dating and I'm just out of the picture. It was at least a couple months ago and I don't even see them in person like at all anymore but I'm still hurting. I want to be over it, but for some reason I find myself still getting sad and angry when I see reminders of them.
Friend, this is entirely normal! Getting dumped by one person is miserable enough - getting dumped by an entire group is going to hurt like nobody's business. You have my deepest sympathies.
This is not really a problem with a solution besides "wait it out." You're already doing the right things by not seeing them in person and trying not to wallow in the sadness, but a few months is NOT much time to get over such a painful breakup!
Be patient and gentle with yourself. Give yourself grace and tenderness when you're sad and angry. Nothing is wrong with you for feeling this way. It's not that you're sad and angry "for some reason" - you're sad and angry because a really sad, maddening thing happened to you! It's okay, and you're okay.
Find distractions - whether it's rearranging your hamster's cage or getting back into playing The Sims or hitting a local concert or foraging for mushrooms. Reach out to friends who are not connected to that group of people. Indulge in some comforts. Consider talking to a therapist or an informal support/venting chat or forum. And know that you will get through this.