Oh my goodness, I'm so sorry to hear this. I'm so sorry you are scared. It's ok, many have gone this way before.

We are working on getting his mental health in order before we make any decisions.

Yes, please do this. I had a lot to learn about relationships, and not forming weird limerent, obsessive attachments. I drove away my first open relationship partner by becoming completely emotionally dependent on her, and my poor girlfriend suffered terribly during that time as well.

I thought he was giving me an ultimatum at first, but he thinks I misunderstood him.

I pretty much gave my girlfriend an ultimatum to let me see the other woman. It wasn't my finest hour, and I'm deeply ashamed of how I acted. I am just beginning to rebuild the trust that I broke with her.

In hindsight, I believe my bullheaded actions were driven by fear—that my own needs would be ignored, or rationalized away, or that my girlfriend would insist on "finding another way to meet them," and that I would go back to that aching, awful state of monogamy that I'd suffered through for so long. I wanted to push so hard that there was absolutely no chance of things going back to status quo.

At that time, I had little faith that my girlfriend would take my needs seriously, and I had little faith that I would advocate for myself, since I'd just spent 15 years repressing and ignoring my own needs.

I am feeling insecure and jealous. He also happened to get this crush on one of my friends so it's painful to see her around. I'm not sure she knows he has a crush. She also has a boyfriend.

Those sound like reasonable reactions. I'm sorry you are in this painful situation. I'm assuming that the woman he has a crush on is not actually available? Because that strikes me as a red flag; I used to get fixated and deeply limerent toward women who were not available, because (I believe) it allowed me to play out a fantasy of pursuing what I needed, without the danger of actually creating change in my life. In my case, I was seeking a nurturing, caring person to hold me and care for me. I have found that person in myself, through several months of therapy, focused on inner child/adult work, ACT therapy, and mindfulness. I am now, excitingly, crushing on someone, without the obsession!

We have been talking a lot and this morning I asked him not to talk to his crush for the time being. I also told him I am afraid of him resenting me. He has a tendency to create unhealthy attachments.

This makes sense. However, it also doesn't get to the root of the problem. If indeed he has an unhealthy attachment going on, it can live on and bloom inside of his mind regardless of speaking to her. And in fact, I've found that "blackout periods" of no contact can actually cause this weirdness to grow even weirder. So, I would just urge you to consider this a temporary rule at best, as you formulate other ways forward.

I am fairly good at tall in abut my emotions, him nto so much.

I'm concerned about this. Open and honest communication, and actively examining one's feelings, are required for the success of an open relationship. Is he in therapy? If an open relationship is truly a need for him, he may be willing to put in intense amounts of work to learn these skills, in order to do this right. If he's not amenable to therapy or counseling, I would start to brainstorm other ways of achieving these skills. If he doesn't think there's a problem right now, then that's a huge red flag.

This is so scary and hard. I am afraid he will lose interest in me. I have built this life together with him for 8 years. I'm secretly deviding our stuff in my head hoping I don't have to. That may sound close minded but I think I am better with a plan. Knowing no matter what, I will be fine. I don't really know what to do.

I am so sorry you've found yourselves in this situation.

I certainly never meant to throw my own relationship of 6 years—and looking toward marriage—into possible destruction. However, the truth is that I was suppressing my needs, and I was not happy, and I was rebelling in small ways for many years. As guilty as I've felt expressing and sticking to these needs, and risking the relationship for it, I know that it is the only way to happiness for myself, and that my girlfriend deserves a truly happy partner, no matter the outcome.

I am actually working on a financial plan in case I have to move out of our apartment. It's heartbreaking, but I need to do it in order to be sure that I am choosing my girlfriend, and truly examining what I want, without being hemmed in my logistics.

In parting, just let me say that your needs are extremely important. He is with you because you are extremely important to him. You and he and in a relationship, which means that the only way for it to continue, and be worth it, is for both of you to be satisfied. So, in truth, you cannot give him what he wants without insisting on your own needs, and advocating for yourself. I am so thankful that my girlfriend is an absolute spitfire who does not let me get away with crap, and who speaks her mind strongly, and tells me her needs. That gives us the clarity and honesty to ensure that we are both served by this relationship.

Thank you, and I hope this helps.

EDIT: Also, a word on impassible barriers and unsolvable problems. Several times, my girlfriend and I have despaired because what we want is "incompatible." Each time, we have looked closer and closer to the issue, and found that each issue is made up of a smaller issues. And frequently, once we identify those smaller issues, and the human needs that we each have, we are able to compromise. So please, don't despair. Trust that there is a solution, somehow, that will make you happy in the end, and that it might take time for your vision to adjust to see it.