Those are good suggestions from LR. Another resource is this board; I've only been here a short time but the perspectives offered here are first-rate.
I am wary of staying in a relationship that is working well for her, but feels awful to me. Isn't that abuse in a way ... abuse to myself?
Yes, it would be if she were ignoring your needs and letting you suffer alone. But from what I read she is talking to you, trying to work with you, and telling you how she feels: that you are the right one for her.
That's not a destructive relationship. It's one that's struggling but constructive. (Just my take from what you've written.)
So maybe you have two sets of psychological needs which are running into each other head-on?
1. You like talking to other women, you like flirting, and even being physical with them. You like the idea of non-monogamy. And I think you're egalitarian enough to grant that if it's OK for you to do it, it has to be OK for your partner to do it too. Fair's fair, right? And that boils down to some kind of open relationship, whether polyamory or ethical non-monogamy or whatever.
2. You have a strong set of complexes centered on possession and infidelity. You described your mother's cheating, your previous girlfriends' cheating, and your own need to possess someone in an almost "trophy" sense. Those are real things in your psyche. They exist.
(Important: I am making guesses based on what you've written, and I could be so
wrong! You're the one on the spot, so take all this with many grains of salt.)
So, then: What do you REALLY want?
Do you want to be a monogamous guy who knows cheating is possible but chooses
fidelity? And who knows that his partner could cheat, but values her all the more if she chooses
fidelity? That's OK. It's completely valid, and leads to beautiful life-long relationships.
Do you want to be a non-monogamous guy who can relate to more than one woman, even feel strong friendship and affection for more than one woman, and who has freed his partner to do the same? That's OK. It's completely valid, and leads to beautiful life-long relationships.
But I suspect that the two psychological poles you have described -- a desire for non-monogamy, and a desire for possession and fidelity -- cannot both be satisfied. One has to move to the back seat in order for the other to drive. If you want polyamory or ethical non-monogamy then you have to find a way to dissolve those issues with infidelity and possession.
You might find a therapist to help you with this. A good one can give you insights in ways that are more direct and personal than you might find in a book or an internet discussion (much as I value the discussions here!).
If you've not been in therapy before, it's worthwhile to note that a therapist should be non-judgmental, with the client's mental well-being as his or her first concern. When I talked to my therapist about being involved with a woman in a poly marriage she was encouraging and positive -- because what I was describing was healthy for me and made me happy. If a therapist starts hinting that any
non-monogamous relationship is cheating and cheating is always bad, then it's time to smile gently and go find a better therapist.
You are in a really cool place in your life! You are at a moment when you can actually choose to become what it is that you want to become! I think there are only a few spots in most peoples' lives when they realize they can do that. And you are conscious enough of your own psyche to have a REAL chance at doing it!