Hi Infern0,
It's nice to see an old face.  Thanks for checking in and updating us. 
I just wanted to say this you experienced loss, I think that it's normal to want something back that you've lost, a r/s with a pwBPD can end abruptly and suddenly which can traumatic to us. I'm just saying that that could be a reason compounded with being obsessed with our expwBPD. 
I used to think about this too. 
It's sort of like what came first, the chicken or the egg. 
I look back at the relationship I had, and cannot recognize myself either. It was madness and I can't believe I was so into that relationship. 
But was I a normal and balanced guy, yet naive to BPD?  Or was I emotionally unbalanced, and thus I acted certain ways. 
I still tend to believe the former more than the latter.  Much of what they do is "crazy making" behavior that can catch anyone off guard.  Atleast that is my opinion.