There is NOTHING wrong with you. You are totally enough and totally fine.
But this is like marriage or kids. Some people want to be married. Some not. Some people want kids in their future. Some people want to be child free. It's a "basic incompatible" -- that is nobody's fault. Everyone has the right to have their future shaped the way they hope/want it. Some things you could be ok compromising on. The color of the couch. Some things -- NO. It is a dealbreaker. You could be on different points in the spectrum of how closed and how open:
monoamorous and monogamous <-----> monoamorous and open to poly friendly <---> polyamorous and polyfidelitous/closed <----> polyamorous and open
Another "basic incompatible" issue could be where you each lie on the spectrum of
independent <---> interdependent <---> dependent
None is wrong, but each has a flavor. If independent is (1) and dependent is (10)... A (2) and an (8) are going to have a hard time being together. The (2) will feel suffocated if they try to meet the "togetherness" factor for the (8). The (8) will feel neglected and lonely going the other way.
But a (4) and a (6) don't have to bridge a gap that wide so they could function ok together.
Polyamory should not be the reason to break up with the love of your life, cheating, hurting the other and so on should be.
He is "a" love of your life. He always will be. But he doesn't have to be "the current, active love of my life" if it turns out that this is the end of the line on this one due to basic incompatible.
Polyamory IS a reason to break up if it is a basic incompatability issue. Take his name out of it for a minute.
Do YOU want your romances to come in a polyamorous shape? Or are you happier/can better thrive in a monoamorous AND monogamous shape?
Could you be happy being monoamorous in a polyship with someone? Where your partner is the shared hinge person in the "V?"
If the answer is "no -- totally unappealing to me!" then as painful as it is... you are dealing with a basic incompatible.
You could be coming to terms with that and dealing with the stages of grief
. It is disappointing to think about, but remember YOU are responsible for your own well being. You HAVE to consider these things in the name of your own LONG TERM well being.
Don't be afraid of some short term break up suffering to gain LONG TERM well being here. You may not want it or like it -- but it could be healthier for you to end the romance and be friends instead. You don't have to lose each other. Be friends and you could lose all these yucky feelings though trying to make a square peg fit into a round hole.
- You trying to embrace polyamory when you really have no desire or willingness
- Him trying to embrace monoamory when he really has no desire or willing.
If you need more materials to read to determine where your willingness lies:
But as a general temperature check on yourself? Answer these super honestly --
1) Are you willing to go there?
2) Do you go there with joy in your heart and spirit?
3) Is it healthy for you (mental health, emotional health, physical health and spiritual health?) and healthy for others?
4) Do ALL THREE of those things have "yes" answers?
If not? Don't go there. Some things in life are not "win or lose" but "this stinks and that stinks. So which choices stinks the least for me?"