About 5 years ago (20+ years into a very good marriage) I felt the call (because it was more than just a desire) to bring another man into our lives. Fortunately, my husband agreed, as long as we could open up fully and play with women also. It took us a while to find the guy because it turned out it was a specific guy I was called to. But in the meantime we started down a wonderful, but often bumpy path to polyamory.
What I’ve most gotten out of polyamory is the better understanding of myself as an individual who is co-creating relationships of various kinds with other individuals. James and I are only a cohesive unit because we each bring our individual selves to intentionally form that not because we are married and therefore are lumped together. I’ve grown so much as a person and so has he — and our relationship has grown by learning to stand in this place of individuality within an intimate relationship. It’s been so healthy! And the sex is good too… although poly life is about way more than sex. We’ve chosen to only see other people together, because we opened up as a way to enhance our relationship, not be more independent from it. But in doing so I still learned a lot about and got a lot of independence because we dismantled so many of the rules and rolls that come with traditional marriage — things we didn’t even necessarily know we’d bought into until we consciously bought out.
Even if you never choose to see other people, books like Opening Up: A Guide To Creating and Sustaining Open Relationships might be helpful because it talks about how to communicate more honestly, how to ask for what you want and also respect the other person’s boundaries, etc. Best of luck on your journey. It was not an easy road for us all the time, but now we are much happier for having taken it.