I really have not budged much

I think you need to put some kind of treatment plan with a time limit in place. I think I was kind of like you and spent about 10 years once wondering what i could have done differently with a FA or DA or a narc or whatever he was. Thing is, I did everything I could and there was nothing I could have done any more. At a certain point we have to understand that it’s only so far we can take it with our effort, and the rest is the other person. And if they are incapable of being in a relationship we need to let them go so that they don’t suffer any more. Listen it’s good for him that he was able to find someone and is trying. I think that’s admirable. But we all know how that will end unless he is in serious therapy.
It’s time to dust yourself off and stop blaming yourself for the failure of the relationship. Even though it’s a painful place to be, it’s also comfortable to be blaming yourself. So you keep the focus outside of yourself in the context of the relationship and not in the context of you. It’s a codependency. See if you can break that tether and while it will be painful, your growth will begin.

You understand that this has not anything to do with that relationship? That you are simply using this construct to perpetuate your low self esteem. You have pathways in your brain that need this repetitive loop to continue. You need to rewire these pathways.

I do....I just had to get the thoughts out of my head so I could get back to the adult perspective.  I am better now...back to a more rational perspective...but man...that was some awful triggering.  Truth is, I really know nothing about B and this girl, other than the fact that he is still listed as being in a relationship.  I think part of what I fight against is this perspective that without work, he will be doomed to repeat his pattern....based on what I am seeing....that does not appear to be happening....so my brain goes into self shame mode instead of being ok with him moving on.  It is like, I want his relationship to fail because then it would mean that there was more then him just not being into me. 

It’s been three years since you split? Have you removed him from social media? Why can you still see what his relationship status is?
I can relate to the obsessing and ruminating, I have this issue too after breakups. It’s trauma. It’s notbing to do with your ex. It has to do with the child part of you that believed that if only you could figure out your parents and be exactly who they needed you to be then they would change and you would get the love you so deseperately need. For myself putting some internal boundaries in place helps; like when I find myself ruminating I will say something like “no, you’ve done this a gazillion times, you never find a clearer answer, the reality is the r/ship is over and it doesn’t matter why, drop it”. This works for me most of the time. You can’t just let that part of you run wild, just like if you had a child of your own you wouldn’t let it go crazy, you would put boundaries in place for it.

At the end of the day it actually doesn’t matter why it ended or why he didn’t want to be with you, the reality is that’s the way it is. I find being AP we have a massive resistance accepting reality and I think that’s what blocks healing and moving on.

Answering in order....almost 3 years since he broke up with me....yes.  Removed him from my social media....I defriended him after he started dating this new girl in August....before then, we were still linked on Facebook....and he would come over to hang out.  I am doing a lot better...but....when it hits me it hits me hard.

I am truly sorry you are suffering about this. But it seems the bigger issue is your self esteem and self worth, as in if you aren't with this person, you aren't worthy or life isn't otherwise worth living. That's way too much power to give to someone else, and that goes for anyone - parents, lover, friend, child. No one should have that power over us, especially someone who isn't looking out or caring for us. You are an individual with your individual gifts to offer this world, more specifically those in your world around you. You are a complete person and you shouldn't revolve around this other person. He isn't the be all and end all of YOU. 

Have you done any inner child healing work? I have and it's powerful, SO very powerful and freeing and liberating.