I'm by no means a licensed therapist or anything, just wanted to say that it sounds very familiar. I used to be VERY anxiously attached when younger, but it ended up being a symptom of my codependency, fuelled and amplified by my pretty much non-existent self-esteem.

The part about mood swings not so much, although I will say it was pretty easy to get me rolling down that anxious hill. I stopped going out with friends almost entirely because I just couldn't take arguments around my first ex's jealousy which went on for hours, with lingering resentment for days (yeah, we were perfect together, what can I say...). This was among many, many... many other subjects, both hers and mine. But this (mostly) only happened within the relationship and the context of our interactions, the seas were relatively calm for me otherwise (save for some "age-appropriate" immaturity and other symptoms of my major issues, although everything was mostly centered around self-loathing and severe doubt, so inward).

If you haven't already, I'd recommend trying to get an official diagnosis around this. I've read up on BPD quite a bit, and the main takeaway seems to be that it's frustratingly easy to mistake it for something else (complex PTSD, for instance), or mistake other clusters of instability for BPD.

I must say, though, you're presenting a lot of self-awareness, and that's a very good sign! Don't be disheartened by the situation, there are always ways to functionally address these things. Having this much self-awareness from the go is a head start!

Edit: wanted to touch upon what you said about having outbursts when you were young, may be able to relate to those as well depending on a couple of factors. My emotional outbursts were mostly as a response to unreasonable standards and some fairly unhealthy parenting methods. I wasn't allowed to release pressure in a controlled manner in general, so I had moments when my valve'd pop off from swallowing all of those frustrations.

It got pretty bad during high-school, when I was catapulted into individuation, while my family was doing everything in their power to lock me down into their unhealthy patterns. One could call what I experienced several times during that period as mood swings, yes.