Hi Blackbirdblue,
Welcome to the forum - I'm glad you found it. I think you'll find that no one here will have a problem with your sexuality - there are both gay and straight people that post here all the time.
And if it helps: I am a woman who was in a r/s with a woman, although I identify as bisexual. No one has ever given me a hard time about it.

I have been involved with two women with BPD. It's a crushing realization - but also a hopeful one. Once you begin to see your patterns you can begin to explore them. I did it in therapy, which was very useful. I've discovered that the reasons for my choice of unstable partners stretches back to family of origin ("FOO" issues.
I'm sorry you're in so much pain - everyone knows how devastating the loss of these relationships (r/s's) are. Their end is somehow worse than "normal" r/s's. For me (and others here that I've read about), their ending opens up a core wound that stretches back into childhood. I know that's what happened to me - I cried like a baby for months.
There are lots of great resources here that will help you process what you've been through. I found it really helpful to read and read and read in order to make sense of the chaos I had lived through. Eventually, however, my focus shifted off her and towards myself - to discover why I chose the r/s's and continued to stay after things became emotionally abusive.
It sounds like you're already there. Please keep posting, you'll find lots of helpful advice and validation from the members here.
(BTW, someone else posted a similar question about a month ago; you may find it helpful:
https://bpdfamily.com/message_board/index.php?topic=303326.0 )