Welcome to the forum!
I have never been married, but I did engage in strictly monogamous relationships all of my life. I was about 53 when I began to identify as polyamorous.
I don't see myself ever going back.
I am currently dating 2 married couples. One couple has been together for 35 years and the other one for 30 years. I am also dating a guy that has been married for 37 years. I know his wife and she approves of him having me in his life, but it has taken many years of patience and time for me to earn her trust and show her that I am not a threat to their marriage.
In my opinion, this lifestyle requires a great amount of emotional maturity. When I entered the lifestyle, it was with a confidence that I have the emotional maturity that is required and although I have had some emotional challenges- I have remained true to my values and personal ethics.
I hope you get lots of feedback from others in your situation. I know there are plenty of people here who have been in your shoes!
The key to life is in being fully engaged and peacefully detached simultaneously and authentically in each moment.