I've always been accepting of the idea for others but knew it was never me.
This sounds like a personal limitation. Which is totally fine to have. People come as they come, they are as they are.
You have a strong preferences for your relationships to be monoamorous and monogamous. The one and only. There is NOTHING WRONG with that preference!
So how does you dating outside your preference pool and you ignoring a personal limit help you attain what you most want?
It doesn't. Strike one with him. He's not compatible in relationship configuration wants from the beginning.
You date anyway. He's been abusive to you and you broke up once already. Strike two. Nobody deserves abuse!
Wearing down your boundaries so he gets what he wants from you? That is not kind loving behavior. You could check the tactics list
to see if anything else has been going on. Maybe it has and you are not mentioning it out loud or to yourself. Again, nobody deserves to be abused.
You say you want to take a cold hard look at your baggage -- could start here reading stages 1 - 5
with leaving abuse. Guard against getting sucked back into the drama. Could guard against "sweetie pie honey bunch" sweet talkin' -- you've already walked away once for A REASON.
When it felt like it was a choice between being with him and my sanity and security, being with him won.
So you put YOU meeting your own needs for health on the back burner. How did you come to choose that? Promises of a better tomorrow?
The cycle of abuse
includes a honeymoon period of fake promises to change. But over time the abuse circle comes back around faster and faster. Are you aware of that?
I just don't know how to give us both the utmost sense of happiness and security when all talk of compromise had brought nothing but heartache and resentment.
If all you experience here is heartache and resentment? Loving him feels hard and like you have to choose between being with him and your own well being? Limit reached. You could choose what is healthy for you in the long term.
Could stop signing up for more and don't be with him. Choose YOU.
It may be hard to FEEL, but the actions for your behavior are pretty clear. Being here sucks? HIs behaviors don't change? Don't be here then. Get out of the way. Love him from a safer distance, but know he's not a good partner up close, allow yourself to be open to loving someone new later down when you have healed. But could reach toward that healing process.
Be very careful and make a safety plan
if you have to. Leaving an abusive person is sometimes very scary/ hard. Talk to your mom straight up about what you are experiencing and ask for guidance and/or access to local resources if you need them.
Yes, breaking up is yucky to feel. But not all choices in life are "win or lose" -- some are "this choice stinks. That choice stinks. Which one stinks the LEAST then?"
I think breaking up and allowing yourself time to process and heal is less stinky that staying here. That way you could give YOU a shot at dating again when ready to find a partner who is more compatible with your values. Someone who does not abuse you. Someone who is ADDING to your sense of well being and to your "secure" and to your "happy" buckets. Rather than taking away.
You deserve to be treated well in loving and kind ways. Not in less than kind and less than loving ways.
You are 20 years old. He may be "a" love of your life. Is he a healthy/safe love to be loving up close? Doesn't sound like it.
I get that if he is among the first loves, it could feel very intense and you could not imagine feeling that way again. But could give yourself a shot at what you really want most in relationship. It is not to be found here.
Life is long. There are many loves out there. Could give yourself a shot at experiencing healthy, loving, kind relationship. Not drama fest.
Hang in there!