Hi Beautifullmess,
Welcome and hello
I'm so sorry to hear what you've been through, it's a lot for your age. Becoming an adult is tough, and 22 can be a hard year in particular because the world begins to expect more, whether you are ready or not to adjust to those expectations. You love this woman, and have been together a long time, plus you both suffer from PTSD. You've done the hard work to restrain impulsive behavior and that is to be commended -- overcoming impulsivity is not easy.
What is difficult about both partners having PTSD or BPD is that the emotional rollercoaster may be pretty much constant, with a lot of triggering and reacting. It may seem normal, even if it is exhausting.
What led to the break? Did she end it? How long since you last talked to each other?
It is not likely you can help someone who isn't looking for help, though you can do things to take care of yourself and build up strength, as well as learn skills to mitigate conflict if/when you two reconcile.
A helpful book that explains some of the dialectical behavioral therapy (DBT) skills and communication tools is the High Conflict Couple by Alan Fruzetti. I believe he also discusses validation, which is one of the cornerstone skills that many of us have learned to use with loved ones who feel fundamentally invalidated. Validation is essentially acknowledging and accepting how someone feels, even if you may not necessarily agree with the content of what is being said. If someone feels sad about being alone, it does not matter if she is not technically alone (since you are right there). What matters is the feeling of being alone.
I hope you'll share with us when you feel comfortable posting more about your situation. The end of a relationship, especially one that has been fraught with fighting and intensity, can feel so overwhelming and confusing.
We are here to walk alongside you as you work through this painful time.
LnL