I agree with Open Eyes in that you should get some therapy yourself in all honesty.

I will say that it's quite unfair to assume that anyone would become a punching bag because the partner they chose is BPD. It is not a given fact that this is the case every time nor is it fair to assume that a bpd person will be abusive, mean or any of these things. I am personally tired of the stigma of not only bpd but bipolar and other mental illnesses and disorders. We need to be careful about promoting this kind of stereotypical thinking. /end rant.

Here's what I see from the OP though. You state that "I want to know what I'm doing wrong in finding women that aren't altogether there emotionally" This seems to imply that you have everything together and that the females you choose are broken and unstable and does nothing to be introspective or self observant.

I do realize that you're asking the question because you realize something is not working here in your situation.

first thought I had was how quickly you moved on from what you call a difficult divorce situation and from an abusive wife and into a new relationship where you not only started dating but made a very significant commitment - getting a house together - very quickly too.

I mention this because it says more about you than it does about your gf that has been diagnosed with bpd. We can look at her diagnosis and could possibly understand why she so quickly jumped into a relationship with you but she's only one part of the equation. You made the same impulsive decision to commit. I do not say this to chastise anyone here, especially not you because frankly I have made enough questionable and/or impulsive decisions of my own but I say this from an outside perspective analyzing what and how you've said about the situation.

I am simply saying, your gf may have issues herself, that may be true but I see someone in you, someone that is desperate to make a new connection very quickly after a break up and that is typically not a sign of healthy relationship beginnings.