Hi Ofeelia, thank you so much for your post, it's very relatable. And it's refreshing and also reassurring to read what you've written.
Almost no one in my life knows about my diagnosis, I've only told one friend...And this, after ten years of the first time I've been told I might have BPD, by my first therapist.
Though I'm still sort of ambivalent about me having BPD, I've had the same reaction as you described...feeling the relief, after hearing it (for the second time in my life).
I've somehow managed to maintain a relationship for nine years with my ex, and during that time I was relatively stable, but also my identity has been somehow merged together with his. This gave me safety. Now, after two years after the breakup I still don't know who I am, even though I try.
BPD is just a way to describe the issues I'm going through, but it's helpful because I recognise myself and can relate to others.

I can so much relate to what you said about sometimes feeling like the only place you could find solace would be a mental hospital. So much. Though when I really think about it, it scares me, because I'm very sensitive to the environment, and usually those places are not calm....But still, I have an image in my mind of a place I'd like to be sometimes, where I would be taken care of when I needed, where I could relate to others and would feel safe to "loose it"...