My partner wants to be nonmonogamous and has cheated on me twice. I don't want to be nonmonogamous or to be cheated on.

My partner and I have been dating 7 months, and they've been honest with me from the start. A few months in the kissed another person and told me, we started the discussion about [polyamorous] relationships. I personally feel very monogamous and that I couldn't be in a open relationship, a few months later they cheated on me with them again but went further, but still let me know. We want to stay together but I don't know how to come to a compromise with them that would make us both feel fulfilled.

You’ve only been with this person seven months. They’ve already cheated on you twice. And you already, seven months in, don’t see a way for the relationship to be mutually fulfilling. It’s time to cut your losses. I think people forget that the reason we date at first is to figure out whether someone is compatible with us in other areas of our life. You have learned a lot about whether this person is someone who can be in a healthy, fulfilling relationship with you. Now you need to act on that information.

The fact that they were honest with you about their cheating seems to be a tactic to make you think that you are obligated to accept it as “just something to work out,” which you are not. If your partner consistently violates the terms of your relationship, that is not okay. Even if they’ve said “hey, can we change the terms of our relationship?” in the past - if you said no, and they stayed in the relationship under monogamous terms, then they didn’t have a free pass to do something just because they said they wanted to. Just “starting the discussion” is not enough. There are some things that “compromise” and “discussion” can’t fix. You deserve to be with someone who respects your boundaries and wants the same things as you do from the relationship.