My uBPDw doesn't vomit regularly, but she vomits often enough that she has stored emesis bags in her purse and in all our cars just in case she needs them. She has talked with her doctor about it and, as you experienced, it was chalked up to something unrelated to her mental illness.
I'm Empty
My husband has those bags all over, too! He has them in the car, in the bedroom, and in the garage. There is an undeniable mind-body connection, I just wonder how vomiting is so closely tied to bpd.