Hello TiredSoul11 and
The roller coaster you describe certainly does sound tiring, especially emotionally. Many relationships where BPD is in the mix, do seem to have lots of blurred boundaries, which can be really confusing and exhausting.
I can relate: my H's kids' mom is uBPD. ~3 months after she and H divorced, she was engaged to H's former best friend (uNPD, now the kids' stepdad). Probably only ~1 year into their marriage, we heard rumors that Stepdad was "helping" a single mom at his work (in a "more than just helping" way). ~5 years ago, I noticed Stepdad acting really close to his new best friend's wife, and I heard some stuff about how they hung out alone. ~2 years ago Stepdad "helped" Best Friend and Wife... right into a divorce. Then Stepdad wanted the kids' mom to be in a throuple with him and the wife; Mom refused so Stepdad is married on paper to her but has a girlfriend... his 2nd former best friend's wife.
Poor relational boundaries do seem to come up a lot when PDs are in play.
While I wasn't involved directly in those relationships, what I can say is -- whether your reasons for your choices "make sense" or not, the feelings you're feeling are real. Discussing if you
should feel a certain way is a different conversation (though still valuable) from discussing that you
do feel a certain way.
I wonder if it'd be helpful to name and work through what you're feeling -- which just is -- before doing more reflecting on "OK, so how did I get here"...?
Your situation does seem like an important one to reflect on and learn from. It might be able to help you learn more about your family of origin (FOO), what they presented to you as "normal relationships", and why you're attracted to certain people, personalities, or dynamics -- so you can be more successful moving forward.
...
So, I think I'm hearing you that you're feeling bad about things -- really ground into the dirt, really low, suicidal, and just at rock bottom.
Are there more things you're feeling, do you think?