Hi hoould5917 and

Blurry "breakups" can happen in a BPD relationship, as many members here can relate. You're not alone here.
I broke up with her because I was going through stuff, but I regret my decision.
What was going on for you?
How did she respond when you communicated to her that you wanted to break up?
I want to know how I get her back. Right now, we’re “friends” and she says she wants to stay single.
That's a hard position to be in -- to have initiated the breakup, and then to have her telling you she doesn't want to get back together. Not a great hand to be dealt -- but it is what it is, and you can work with it.
The key is probably going to be, as counterintuitive as it sounds, working on yourself and changing yourself.
Whatever the dynamic was between the two of you when you were together, something wasn't working -- the relationship broke. Going back to that with no change on either side means you may just repeat the past.
The only person in this dynamic you can change is yourself -- not her. While there's no guarantee of "just work on your own mental wellness and you'll be rewarded with her returning", it's the only change you have 100% control over.
Have you had a chance to check out our article on
What Does it Take to Be in a Relationship yet? Read it over and let us know what stood out to you. Relationships with pwBPD aren't always intuitive, so it's important to learn new, healthier approaches if you want a reconnection to have any chance.
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Are you in any kind of counseling or therapy right now?