Really activated and don’t know what to do

I am a graduate student trying to get through the next week of my semester so I can finally have a break. This semester has been incredibly difficult because I also have a part time job. Which means that I am doing some type of work seven days a week. In addition I have complex ptsd and while I've come a very long way it can be challenging to manage. Therefore, I've not gotten to pursue sex and dating in the way I've wanted this semester.

I've been working really hard to get through it and planning to finally join dating apps again over the break. Today I had a very activating experience when talking with my (33F) partner (33 NB) about their day. They informed me that they were going to a friend/lover's birthday sex party. And I just felt my stomach drop. The grief and comparison that I feel like I've been holding onto for the last six months just poured out of me.

I know they can sense something is up but I haven't mentioned it yet. I do think I need to take space over the weekend to process, sit with my feelings, and take care of myself. The thing is that when I'm activated because of past trauma I tend to pull away really hard. I don't know how to talk about this with them because it's bringing up a lot of shame. I also don't want to be around them right now because I feel very vulnerable.

I'm happy that they get to have these experiences but it does bring up an immense amount of pain related to things I haven't been able to pursue. I've asked them in the past not to share specifics about the sex they're having so they won't share details with me about this party. Yet I'm still having a really significant reaction.

Would it seem reasonable to ask for space for the weekend and let them know I'm not ready to talk about how I'm feeling yet? I figured we could try to at least check-in on Sunday night.

TL,DR I'm in the last week of my semester and mentally/physically exhausted. I've had to sacrifice a lot of free time for work and school this semester. Today my long-term partner shared that they're going to a friend/lover's play party tonight and I broke down. What feels like months worth of envy and grief are coming to the surface. I don't know how to talk to them about it and think I need space.

Edit: Thanks everyone for your support. The past several months I've felt like a really bad poly person. I especially appreciate those who could relate to what I'm experiencing.