Poly is one of the issues, though not the main one. The others have to do with some work-life balance and other parts of the relationship that have gotten somewhat off-kilter as we've both been absorbed in other things. The fertility issues certainly play into it as well, as we both are dealing with that grief in our own ways.
They are all things that have been discussed, but aren't resolved completely, and I do plan to continue to bring them up and work on them, and have a time set to discuss them again in a few days (after a big deadline). Overall, I feel like we are strong and the relationship is mostly good, but there is still work that needs to be done or we might not be so good down the road.
I have been very clear about keeping our issues separate from the dating issues. For example, too many late nights at work means not enough time together. I do NOT want to date someone else because I feel I get too little time with you. I don't want you to feel I am abandoning you for someone else. I also don't want to cut into the limited time we do have together right now. How do we negotiate this around our schedules and that of the person I am interested in? Etc.
I guess I am feeling like I am asking to balance our relationship by fixing the problems, and at the same time asking to unbalance it by starting a new relationship. I am also feeling like this new relationship has been very slowly growing over a couple of years, and I don't want to disrupt it right now, when it is finally gaining momentum. I will, of course, if needed, but was hoping to hear how other people have successfully juggled something like this. Or not.