Hi Chasing_Ghosts, a relationship with a pwBPD will make you do that. I am not at all surprised by your statements. You are probably well aware that a breakdown after a recycle is worse.
Your post was difficult to read. I felt I had to respond.
BPD tends to have terrible implications for a non and even worse if you have your own issues... .which, let's be honest... .we all do... .and if they are triggered by the illness that is BPD... .
I know it is not easy to recover but I feel you have enough self awareness and awareness of the situation to do just that... .make no mistake it will take time though. I agree with Narellan, how and what you are feeling is completely normal... .and a part of the recovery process.
I relate to what you are saying about your seeming inability to breathe. When I separated from my exBPD partner (20 years/3 children) I felt like I had a sumo wrestler sitting on my chest. I am not joking. I could breathe out but it felt very hard to breathe in... .I can't remember when he got off exactly but I do recall the enormous sense of relief... .like a weight had been lifted off my chest. This was a turning point. I anticipate the same for you.
Don't give up. Know that things will get better.
My prescription for you:
Take it easy on yourself.
Keep life simple. Do simple things as Narellan has suggested.
Get as much rest as you can. This is important.
Try not to analyse the rs breakdown too much too often.
Find or reconnect with friends.
Try to eat healthy if you currently do not.
Pretend you're OK... .put on a brave face.
Maintain boundaries with the exBPD if she tries to pull you down.
Smile.
This is not a doctors advice but it's the best I can do.

From someone that once lost EVERYTHING.
Here's to you. My friend.