Hey Annie D,
A breakup with a person suffering from this disorder is so very difficult to work through. The nature of the bond is loaded from both sides. It takes time for the initial pain to subside.
I would suggest going back to the very basics. When my partner and I split up, in typical BPD dramatic fashion, I was also recovering from surgery and I was forcibly struck by the similarities. I needed to be very gentle with myself and concentrate on eating, sleeping and getting some reasonable exercise. There will be plenty of time to figure things out when the emotions aren't quite so raw.
As ChrisRD mentions there is a physical component to this recovery.
Be gentle with yourself, go slow, avoid making huge decisions for a while and maybe take a look at this workshop.
TOOLS: Ease your pain by reframing your thoughtsbabyducks