To start, IDK if I'm looking for advise, or just to get it off my chest at this point. Advise is welcome, though I will push to work past this, and not just end things.

So, I (26M) and my partner (28F) and our partner (28NB) have been together almost 2 years now. We are in a triad, and please, no triad hate.

So I struggle with being polyam when my depression and anxiety get bad, which it has been, due to stress around money, COVID, ALL our our mental health (my partners both have some really serious ones, BPD and schizophrenia respectively) as well as regular health issues. And so we go through bouts where we are more reclusive and stick together more then we branch out. My partner (28F) is the only one of us who is more then just dating lightly at the moment. She has a boyfriend, and she dates quite a bit. However, since we, and specifically I, have been struggling so much with everything, it's caused a spike in my jealousy, feeling like I'm not getting the time, attention and support I need from my partners to maintain our household properly (I'm the only one who works a full time job, due to physical and mental health restrictions, which has never bothered me, it is just stressful at times).

Now, since I've been struggling so much, (28F) suggested that maybe we dial it back, focus on our triad, and only date lightly to try to help me. She suggested it of her own free will. So she said that she absolutely would not be sleeping with anyone, except for us, until they were both able to help me put back together better mentally so I can in turn support us all properly this included her boyfriend, who was a new comer, and I was told didn't really care about sex right now, as he is married, so she said he was happy to comply when she brought it up). I was happy to agree. Didn't really affect me, I haven't had the time or energy to put into even dating outside the house.

This was a few months ago now. Many times since then, I'd broken down, telling her I felt like I was restricting her and that if she wanted or needed more, that I just wanted to know about it at least after, as was always our agreement from the start of the relationship, just for health and safety. She has always been so wonderful and so reassuring to me, telling me we were more than satisfying her sexually right now, and that anyone she talked to or dated that pushed the line could either wait until she told them she was ready, due to the situation, or if they pushed too much she would just drop them. We had these talks time and time again, and she always told me the same thing. That she loves me, it doesn't matter, and we have the rest of our lives to date and sleep with others. I know, it's not the best or healthiest thing to put the restrictions on, but since she enacted it temporarily and it was until we all felt ready, it was perfectly okay for us.

Cut to yesterday. Or the day before now I guess. I work 12 hour overnights, so my days are screwy. But we were cuddled up all together before I had to leave for work, as we usually are, soaking up the last bits of time together, and trading memes occasionally, the usual stuff. Well, she shows me a meme. And perfect as a movie scene, a message pops up at the top of her screen, and I instinctively go to read it, as most people might. It twisted my gut so hard and so fast. It was from a friend she was going to hangout with later, and I'm paraphrasing, but it was along the lines of "yeah, I'm ready to fuck, my last test was recent" and she pulled her phone back (she was holding it in front of me) swiftly but calmly hoping and assuming I wouldn't have read it. I saw her give me a subtle side glance when she thought I wasn't looking. I was in shock. My mind was racing. He was just a friend. She had said she had zero interest in him, but here we were.

Rewind a little now. I was aware that she had gotten nudes from him, because she would kinda roll her eyes and share that sort of thing sometimes. She said it didn't bother her, she just didn't engage. I trusted her. But I had asked back then. Told her that if she wanted to, as always, she was of course free to pursue. She always said she didn't have any interest, even the other day. She assured me that if she wanted to do anything, she would tell us, at least after.

Back to yesterday-ish. I was freaking out inside. I should have said something then and there. But I was shocked. And I wanted to think better. Wanted to trust her so bad. So I let it go for now, tried to calm myself. Work was hell, imagining and reimagining everything that I knew was happening... I was hollow. Broken. Hurt. It had set in at that point. After she got home and showered, she acted like normal. Didn't bring anything up. I asked her how hanging out was. She kept it short and light, saying they just talked and she got to see his nice suits. Then she changed the subject. Didn't even bat an eyelash. I wanted to be wrong, but I couldn't think of a way I could be. So I stewed all night on it. When I got home, I walked the dog and checked on my partners, as I always do. I tried to initiate sex out of pure desperation. Waking either of them up for sex after work isn't an uncommon thing we do. She rebuked me grumpily, which only set me over an edge of panic. I set myself up for that one. But it also showed me again what I knew. Now... The bad part. I'm ashamed... Extremely ashamed of myself for this. I went through her phone. We have all always had an open phone policy, out of courtesy, but haven't invoked it. I know while she was sleeping was NOT the time. But I did it anyway. And I found what I was looking for, clear and plain, in no uncertain terms. All the messages. And it hadn't been spur of the moment passion. She offered it. For his birthday. At least she made sure he was clean I guess. Or so he says. I don't trust other men. As a man, I feel that I'm pretty justified in saying men are shitty. Everyone is justified in saying men are shitty. Anyways. I found that. I was so sick to my stomach from what I saw and how mad at myself I was/am. And now I'm doubting months worth of hangouts. Especially the friend that she dated before and slept with, about 7 months ago. She told me right after, no issue, and I was happy for her at the time. Speaking of, she was there tonight. And now I can't stop thinking. And I KNOW the friend she's going to see tomorrow has mutual attraction. But again, she promised it won't go anywhere and that she would of course tell us. But I can't believe her. I just can't. It's fine. I'm a husk. I'm empty. I'm seething. I'm terrified. I'm so broken inside. Why? Why would she do it? I'm upset it happened, sure, but I'm so much more upset that she won't admit it or say anything. Why won't she? How can she continue to act so normal and tell me she loves me. Why. I'm just... Raw.

And yet, despite that, everytime she messages me when I'm away at work, I crack, and break, and just feel all my love, and all my feelings just turn to exhaustion and I just talk like we always do, just happy to get to talk to her. I need to confront her. After tomorrow, I have a few days off before I work a few more days. I need to tell her I know. I NEED to confront her. But I don't know how. I'm scared. I'm so willing to move past this and work, but I'm so scared she's going to do it again, or leave... So yeah. Thanks for reading my rant I guess. Please don't judge any of us too hard. We are trying. And we love each other.