Hi PleaseJustStop,
I am very sorry to hear that you and your fiance are struggling right now, but it is great to see you reaching out for help and support - a very brave and scary thing to do!
This site is a support group for those who are or were in a relationship with a person with BPD, so many of the posts can be triggering to a BPD sufferer. There are resources of the type you're seeking. Please check out
Resources for BPD Sufferers.
I wish you well on your journey.