I'm curious about your statement that you think you may have a different or another mental illness. BPD = borderline personality, or bipolar? Based on my own experience, I would say to try not to get too hung up on labels, but focus more on specific symptoms and what you've tried and haven't tried for those symptoms. There is a lot of overlap with some of these so-called disorders, so it is not unusual for people to be diagnosed, for example, with borderline personality and/or bipolar, and/or PTSD, and/or substance use disorders...
For me, it helps just to recognize when I'm suffering, and to have a plan (other than drink or drug) to do something about it. My recovery started with awareness of my symptoms, as well as my strengths. From your post I can tell your are no dummy, and you're well aware. Congrats on two months sober. It get easier when we stay clean.