No journey is without bumps in the road. But I think you are feeling extra pain because maybe you guys just opened up without laying out any kind of framework for dealing with wants, needs, limits, emotions popping up, conflict resolution, etc FIRST?
In my world? I lay it out crystal clear on rights and responsibilities.
I also lay it out for conflict resolution
I also lay it out for what type rships I'm looking for.
I don't get the vibe that you guys were on the same page of what "open" means though. He may have thought "open to date to find serious GF" and you may have thought "open to date and have casual sex like swinging" or something?
Take a time out to sort yourselves out, make sure you use the same vocab, are on the same page, etc. You have thought about your wants and needs and limits and expressed them to him so he can help meet them so you can feel secure and good about your polyship arrangements.
Have you been through
There's lots to read there. Perhaps help you get your thoughts together?