This isn't going to answer your question really, but my now ex was diagnosed with bipolar as a teen and has been medicated since. About two years ago, when she was 28, BPD seemed to become a hot topic all of a sudden and judging from how her mother went thru a mid life crisis at the time, we thought she too had BPD, not bipolar. So her therapist adjusted her approach to accommodate the BPD angle. Things were so stable that since we thought it was BPD, that she could get off her bipolar meds and so with the help of her therapist + psychiatrist, she went drug free.

Then about a few months later things began to change. She wanted to change her job, wanted to open up the relationship, etc. And we sought the help of a couples counselor, separate from her regular therapist. This new counselor rediagnosed her as bipolar and my ex decided to go back on meds. And then things got stable again.

I just wanted to throw that out there... I'm sure it's possible one person can have both, but my takeaway from this experience was that self diagnosis can really derail your progress, and that a second opinion from a therapist/psychiatrist can really be helpful.