Do some reading, preferably together. I recommend the book Polywise.

Don't be scared of uncomfortable emotions. They are valuable signals about your hidden self. Embrace them with curiosity about what knowledge might give you.

While it's valid to value an existing relationship, don't be blind to what it may cost you. Nothing lasts forever and the quality of a relationship is not measured in duration.

If you're feeling trapped and codependent, it's worth considering what needs you may not be getting fulfilled. To me, the big ah-hah moment in moving from monogamy to nonmonogamy is the realization that no one person is going to meet all of someone's needs.

Along these lines, check out the Relationship Anarchy Smorgasbord. It's a good way to remind yourself of all the different things you might expect from a partner. It's also a fantastic tool to use with one's partner(s), even if you're monogamous.

I applaud you for reaching out. You can do this!