Actually... . I had originally typed up this whole thing about how they seem to have a healthier longer (it has been awhile they are together) relationship. They travel together, she is apart of all his social life with friends and co-workers which I never was.
So even though I am not blind and I know its not as picture perfect as it seems, I can safely say I am the one who knows about his BPD. That is the confusing part.
hmmm... . wait,
I don't know your story so I might be a little off here, and in case, I apologize.
But... .
what are the relevant pieces of information here?
1) he made you suffer more than anyone else in the past? (I think so, otherwise you would not be here)
2) you are not together
3) you suspect given 1) he might have BPD
what is the confusing information for me that I read your post?
4) would you like to be back together with him given 1) and 3)?
if the answer to 4) is NO,
then the following information is irrelevant:
5) he is with someone else
6) he seems to be happy
7) you don't know if he is really happy
8) her new gf does not know of his BPD traits
if the answer to 4) is YES,
then you should loop over 1)-3) for some time, read these boards, talk to your family maybe a T, and I believe your answer to 4) will become NO.
In any case, 5)-8) are irrelevant for you, what is relevant for you is 1)-3) to answer to 4).
Yes it is difficult. Because 5)-8) touch you inside and raise doubts about yourself in the r/s with your ex. The point is that you don't have control over 5)-8), while you have control over 4).
And it is not rational to wast your energies thinking over stuff you do not have control over, while it is rational to use your energies on stuff you can control.
This is my view, and as I said, I understand the way you feel. The idea of NC I think is to not know 5)-8) in the first place.