Yeah that is all very true. I am notoriously excellent at being super hard on myself.  At first he was calling and texting/ emailing nonstop and now he's just gone. I feel crazy for feeling blindsided. Like, of course this is how this was all going to play out. I just had so much hope and faith. Heard it gets better with age.  That it is curable or at least can become much more manageable. Wanted so badly to help him get there. I just was being treated as if I didn't matter at all and I was asking for the bare minimum. I know there is no logic. I know crazy makes crazy. I am having a hard time wrapping my head around it all. I regret trusting certain people. Yes I am a human who was pushed to extremes but I still beat myself up for failing so epically. And i miss the good times and I miss his dog. It's all so sad.

I think you're onto something here.  He tries to erase you from his life because it hurts him too much to think about it.  He can't stand to admit that he played a huge role in creating chaos, because the shame eats away at him.  It's easier to tell himself that you're a monster--to blame you, instead of take responsibility.

While it's typical for pwBPD to cut you out and enter a period of estrangement, it's also typical for them to re-engage.  Usually when they re-engage, (i) they pretend like nothing happened, and (ii) it's usually because they need something.  The needs might vary from person to person, but if you read these boards, typically they need emotional support and/or money/housing/logistical help.

Just my two cents.

If you want raw honesty, it's a little of both.  BPDs run from the pain and often lash out while doing so.  They can't stand to admit fault, even though they know that they played a part, because it eats them up inside and makes them wonder what the heck is wrong with them.  So if he has to choose between focusing on you (which hurts), himself (which hurts more), or some new girl that is giving him positive attention (which feels great), it's a pretty easy choice to make.  Run from your problems, blame others, and live a happy new life (until that falls apart and you're doing it all over again).

Did you do things wrong?  Yes, you're human and we all make mistakes.  But you shouldn't focus on that because you didn't make the kind of mistakes that makes it okay to cheat on someone, spy on them, give them no privacy, be verbually abusive, etc.  You must see that and accept it for what it really is. 

You were dating someone unstable and they treated you badly.  I fully understand how much it hurts for the relationship to fall apart, but you did your best and you will learn from this experience. 

I know that i have a particularly high threshold when it comes to being abused which is not a good thing at all. But it does tend to skew my view and downplay how bad things can get at times. He definitely does have bpd, no question. I am trying to figure out  just how bad his is. What kind of abuse did ya'll put up with?
He was still calling and texting at first and then just fully disappeared which is also probably for the best but I can't help but feel angry that he could just cut me out of his life like that. That he could delete every single thing we shared together. Is it all just because it hurts him too much? Or is it because he has decided that if am a monster?

Yes, there were frequent breakups but always initiated by her. First time was only after a few weeks, when she just walked right past me as I was waiting for her for a night out. That came as quite a shock, especially as I'd never heard of BPD before. I put it down to moodiness and insecurity.

Turned out she'd had a bad day at work, decided I wouldn't be happy with that for some reason so she breaks up with me before, in her mind, I break up with her. That's how a BPD mind can work - seeing things which just aren't there. We were broke up for a few months, though she still came into the pub to make sure I could see she was there. Premeditation, she knew exactly what she was doing.

After me chasing her and us getting back together, that was just one of many meltdowns by her for various reasons, none of them being my fault. Argument with her mother? Break up with me. Getting beat at pool? Break up with me. I talk to the barmaid for too long in her opinion? Break up with me. I'm sure you've experienced similar.

4 years of this but her last meltdown was the one that made me call it quits and I never contacted her again. She was worse than ever, saying the most ridiculous things and she seemed close to getting violent which I'd never seen before. Maybe I was finally seeing the true person and it wasn't something I was prepared to continue with, not matter how much I still cared for her.

Did you guys ever break up?  If so, for how long?  It was also my birthday recently and she did not text me to wish me a happy birthday.

Sometimes they just 'switch off'; there's doesn't have to be arguments or a big meltdown, they just simply act as if they've never known you. My ex would simply close off at times and I never knew whether she was genuinely doing it as a result of her illness or if she was just playing some premeditated game. I suspect a bit of both.

I wish we could offer definite advice like 'if you do X then it will result in Y' but with BPD it's impossible. They never know how their emotions are going to run at any given moment so how can we ever know and take the right action?

I never knew if my ex was even going to turn up most of the time or whether something had happened at her work or family that day which she would blame me for and not turn up. She would break up with me and threaten to see other guys if she lost a game of pool (which she was brilliant at but a very bad loser made worse by her BPD).

The thing is, I’ve given her many opportunities over the last two months to come to the table and work things out and she hasn’t agreed to thus far.  She’s such a confusing person.  If she has met someone new I think it’s within the last week, so very recently. 

She was cold and indifferent because...well, you already know why.  She told your family member directly.  She walked away so you'd chase her, and when you didn't it hurt her feelings.

But then it gets complicated.  After waiting for you to chase her, she probably started looking for other options as well.  That's a very BPD thing to do.  You already mentioned she was "sexting" another guy so it's not that big of a stretch to put two and two together.

Even if that's the case though, it doesn't mean it's over for good.  It means she's distracting herself until she becomes convinced that walking away was the right thing to do.  That could change in time as well and she could reach out.  You already know this part though; it's unpredictable with the timelines.

Let's say she calls tomorrow though, she comes over, and you see on her phone that she's still sexting another person.  Then what?  I think you'd be better off preparing for that and where your morals stand than if she'll reach out at all.  Because if you take her back but she's still being unfaithful, then what's the point?

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About a year.  The thing that worries me is that she seemed not upset or emotional,  just apathetic, indifferent disinterested in talking to me and just left me on read when I told her I’d like to see her in person to talk.