I am going to try to be as concise as possible with the summary of the relationship, and catastrophic breakup, but trust that many of the details left out for the sake of brevity are consummately brutal:

(M37, F29) The breakup was about a month and a half ago, and total duration was just under 4 years. She is in medicine, so I was with her through the last 2 years of med school, traveled with her to 6 different cities as she completed externships, internships, and finally settled on a staff position at the beginning of August. This was to be our final move after all of the hard years of her not making much (me covering most financial expenditures), her working insanely long hours, moving and traveling non-stop, etc. We had finally made it, and the good times were about to start! She started sleeping with the medical director within 4 weeks of arrival in the new city, finally making a paycheck, while I handled all of the move-in tasks.

Early in the relationship, we had tried a one-sided open relationship (she could be with women, and I would remain monogamous to her). To say it went horrendously would be a disservice to the extreme behavior she exhibited. Prior to embarking on this ill-fated attempt at open-relationship, I read every book there was on the subject, talked endlessly with her about how it should go, what the rules were, etc... but as soon as she was with someone on a date, all agreements went out the window, and she did whatever she wanted (and holy fuck did she do absolutely whatever she wanted)... then lied about all of it for months on end.

We attempted the impossible: to reestablish trust after repeated betrayals, and I trusted her email that "no matter what, you can bet on the fact that I will never treat you that way again." I read every book there was on rebuilding trust, healing betrayal, etc, while she finished medical school. Just before we made the final move to the city where she settled on her staff position, she brought up wedding rings, and how we should use her grandmother's stone and save for a house. I told everyone I knew that I planned to propose to her by the end of the year.

Then suddenly, 6 weeks into the move, when I had just about finished making the apartment homey, she broke up with me, with reasons that seemed to lack substance ("I don't like how you deal with stress" being a main one) and despite all of my pleas to go to therapy to handle stress better - \*much of the stress was because I was handling everything from moving, to finances, while working 12 hours a day to make it work through her final years of school, etc\*, she said there was "no chance." In addition, she suddenly was acting with complete resentment towards me, palpable contempt. It was all so disorienting.

I asked if there was someone else, and she vehemently denied it. She continued to lie prodigiously as I scrambled to figure out what city I should move to, what to do with all of the furniture I bought, etc. Finally, after 10 days of her gaslighting me ("you never trusted me, of course I'm not sleeping with someone, I'm done trying with you"; "you always thought the worst in me, of course you would think that", "I couldn't even think about being with someone else right now", etc), I looked in her phone, and not only was she sleeping with her boss, they were headed on a road trip to meet the parents while I was still physically in town, scrambling to figure out my next move.

When I finally revealed that I knew what was happening, giving her all of the chances to be honest before the final reveal, begging both her and her best friend... her reaction was of furious anger towards me. I waited in my car for 2 hours at 3 in the morning (she had just gotten off a shift), as she packed to go on a trip to meet her lover's parents, despite the fact that I begged her to be quick. That was the last time I saw her, and she not only stiffed me on money despite the fact that her company gave her relocation costs (I paid for everything), she then blocked me on everything.

The "closure conversation" I received was prior to me finding out she was cheating on me, and I blamed the breakup on myself - after all, if there was no one else, and she knows I would do anything for her, and I was good to her... it must be my fault. To this day, even though she manipulated me into saying it was all my fault, she stands by that truth.

I never got an actual discussion about what transpired, and she is firmly of the belief that apparently sleeping with her boss has nothing to do with the swiftness of the breakup, and everything is my fault. She has gone as far as to accuse me of being "emotionally abusive" during the breakup to multiple people, as I saw in her phone. I have since spoken with 2 therapists about this, showed them all text communications during the breakup, spoke to my ex's, and all agree this is laughable, and bpd projection.

I'm feeling the need to write a letter to explain my feelings, wish her the best, as I'm really not good with leaving things on a horrible note. There's no reason for it. I am on good terms with every person I ever dated. But I know the common wisdom on Reddit is to never send a closure letter, so I'm torn. There's so much left unsaid from my end, because I was never given the chance, unless what was coming out of my mouth was that everything is my fault. I just don't know how to just drop such a significant person like she never existed, and on the worst of possible notes.

I didn't even get an intimate breakup, as I found out she was texting with (triangulating) with the new lover (the medical director) simultaneously as she was breaking up with me. I knew something was awry, but she swore up and down that there was no one else, and it was simply that "I thought you were my person, but you're not."

The hardest part is that she wins across the board: She took a substantial amount of money from me, doesn't have to feel ay of the sadness or loss of a breakup, feels no guilt about how she handled things despite previous promises, gets transcendent sex (as I unfortunately had to see in the phone), gets sympathy from the new lover and coworkers since I'm the big, bad "emotional abuser", gets the perks of dating the medical director (better schedules, preferential treatment, etc)......... and my life is decimated, I have nothing because I left all furniture with her, and I have no idea what to do next.

TL:DR: Person I thought was going to be my wife cheated on me with her boss, lied to me about it incessantly, blamed the breakup on me anyway, and didn't give me a chance to talk about it, nor say "sorry" in any way. I want to write a letter to express my feelings, as I was not given the chance to. I do not care in the slightest that this would make me look "crazy" or something, because they've already labeled me as such to each other, and deemed me an "emotional abuser".