I've been married for nearly 11 years. It was mono to start.
It was frustrating and heartbreaking and I felt stifled and broken (often used the Eagle in a cage example).
My life ONLY improved when I did the following:
I quit pretending to be something I wasn't. I compassionately explained that I had failed in THIS marriage, because I simply hadn't done the TRUE "dirt work" before hand. I wasn't cut out to meet the commitments I had promised to.
I explained that yes I do love him. Yes I always will love him, but I can't be the kind of wife I PROMISED TO BE.
I gave him the promise that if that meant divorce, I would respect that and honor him by NOT dragging him through court b.s. with our 4 kids, I would settle with him and ensure that I NEVER put in place something that would make his relationships difficult (like moving away causing battles over custody).
I then committed to having NO LOVERS WHO WERE NOT FULLY ACCEPTING OF WHO I TRULY AM.
THEN I went about discovering WHO I TRULY AM. Because "being poly" is only ONE aspect of a person. I identified my TRUE "world view", values, morals etc. MINE-not the ones I thought were mine because that's what I had lived my whole life. (this required a great deal of reading).
THEN I started looking around my life to see who/what was in it that was COUNTER to my TRUE world view, values, morals etc. I started gently "weeding these out".
Additionally I began looking at myself to see what actions I was taking that were counter to my TRUE world view, values, morals etc. I made a list and one by one I have been "discontinuing" those actions (hard work that one!).
I also began looking for what things I wasn't doing that I SHOULD be doing-and began DOING those (like working out, eating healthy, being considerate FOR REAL ALL OF THE TIME, controlling my emotions instead of letting them control me, controlling my behavior and not saying/doing ANYTHING that was counter to those goals).
It sounds like you REALLY need to stop yourself and take a long hard look at what it is you REALLY WANT FOR YOUR LIFE. Not for the bedroom, for your LIFE.
Do you want casual sex partners, a great job, a small studio apt, a fishtank full of expensive fish...
Do you want to have a poly-fi relationship with two women, or 3 women and 2 men, or 6 men and 4 women or (just made all that up).
Do you want to be free to have a couple deep meaningful sexual relationships AND some deep meaningful non-sexual relationships AND some casual sex partners?
Do you want to live in the city? Country? Another country?
Suburbs?
Do you believe in a "bigger picture" like the "Gaia Theory" or "deeper enlightenment" for everyone??
Do you have children you need/want to stay available to limiting your ability to BE where you prefer? If so how are you planning to negotiate this in the long term?
What do you want to impart to them in regards to relationships, lifestyle etc? Would you like them to NOT make the "mistakes" you have (and are)? Do you want to impart to them the importance of continued learning after formal schooling ends? Or that loving people unconditionally is more important than having what you "want"? Or that you must always be true to yourself?
(no push for any given thing from me, just trying to brainstorm thought provokers for you)
The thing I would suggest, you said you started a family, so I assume you have AT LEAST ONE child, and you were married 9 years and been on your own for a little bit.
SO it stands to reason that the "at least one child" isn't grown yet-
Therefore I wonder if you've considered what you are teaching them with your ACTIONS.
For starters, divorce is devastating, more for the child than the parents-they need EXTRA support, reassurance and attention from both parents to ensure that they INTERNALLY feel that they will remain secure, even though the biggest security they had has fallen apart (their family support system).
But more then that, they need to know "what does a great man do as an adult" and "what does a great woman do as an adult".
OBVIOUSLY you can't teach them what a great woman does.

You've implied already you aren't a woman!
BUT-if you insist on allowing women who ARE NOT suited to being with someone like you, to "punish" themselves AND YOU by being with you, you teach them that there is something WRONG with your type of "loving" (poly-ness).
You also teach them that relationships aren't "sacred".
(not lecturing on being one way or another per se, but if you and/or she isn't happy with the relationship but you stay in it, that isn't "sacred", even a one night stand where both people leave with no regrets is more "sacred" then a lifelong marriage where one or both partners is obviously miserable)
Additionally you teach them that THEIR NEEDS DON'T REALLY MATTER, becuase you aren't standing up for your own. AND you teach them that EITHER their mother isn't worthy of respect OR you weren't worthy of giving it and/or are a liar.
BECAUSE-you left her "due to being poly by nature" but you are with someone else who can't accept that so OBVIOUSLY there was either some other issue OR you are just f'd up.
It may seem like a "young" child wouldn't be able to figure these types of things out-but I assure you, they do.
I did when my dad left my mother (for good reasons I might add).
My son did at age 4 when his father left me (I was cheating). I know he did because he was VOCAL to his father about it. When his dad left it was obvious to our son (we didn't fight, we remained VERY amicable) that his dad was mad "or he wouldn't have left the house" as he said.
He told his dad, "you tell me and D (his older 1/2 brother) and A (his older 1/2 sister) that if we have a fight we need to get over ourselves 'cause we're family. YOU and GreenGecko (log in name here for confidentiality) need to get over yourselves 'cause we're family!"
A very 4 yr old view-but the underlying message was "dad you are a liar and I SEE IT".
It broke my husbands heart to say the least (about the same time it caused him to lose his temper because for the first AND ONLY time he thought I must have been "talking shit" about him to our son-but I wasn't).
The bottom line is-kids DO "create" themselves based on what they see their parents doing.
You are disrespecting YOURSELF and the other women AND the "unsuspecting boyfriend" with your actions. Your child(ren) will pick up on that and it will color their future too.
YOU DESERVE BETTER.
The women deserve better.
The other boyfriend deserves better.
You can't do much for making the women or the other man going out and seeking better.
BUT you can hold yourself to a standard that respects yourself, your needs and your rights.
You can hold yourself to a standard that shows your
child(ren) the types of relationships you want for her/him.
IF you have a daughter(s),
you can show her how you expect a man to treat her and how you want her to treat men (see below).
You do this by treating her mother (as your "ex") AND ALL OTHER WOMEN with respect-even if they don't respect themselves enough to insist on what they need (don't date women not cut out for poly) and treat your ex with the loving (not sexual or misleading) kindness you would show your mother.
IF you have a son(s),
you can show him how you expect him (as a man) to treat women and how you expect women to treat him, by doing the above AND by insisting on being true to yourself and only being with women who are healthy and whole and capable of compEmenting your life, not women who bring unnessary drama, headaches and heartaches to your life.