It can be very difficult to tease out what is PTSD or borderline and what is bipolar. I have been dx'ed with all. From fourteen to 20, I was a mess. Hospitalizations, state hospital, residential treatment, alternative school. When I was 19 I received the dx of bipolar 2. I said that's not even possible as I was never happy, thus no hypomania. I felt It was definitely PTSD with borderline traits, because all my emotional anguish directly stemmed from childhood events. Eventually in 2006 I spent six months in a trauma treatment outpatient program and did some good work. It took me a couple more years but I finally was able to accept and forgive everything that had gone on. And I was great for six years. Sure, I would have a couple I months where if get depressed and wonder if the docs were all right about the BP, but it would always go away so I would never seek treatment.

My son was born three years ago and everything began deteriorating. But I still never believed I had BP because again, I never felt euphorically happy. At leat not that I recognized. Looking back I can see that yeah, maybe. Fast forward to a year ago when everything went crazy - depressions got deeper and more frequent, and hypomania progressed to full blown mania, and I finally sought treatment.

My point is I refused to believe BP until I had dealt with all my trauma in therapy. Once the distorted thinking and trauma reactions were no longer holding me back, and the BP symptoms became unmanageable, I had no choice but to try to accept the dx. You can absolutely have concurrent disorders. Therapy is your best chance at figuring out what is attributable to what.