i was about to recommend
the other thread but i was going back over and noticed that you had already posted in that, aha!
i had been treated just for depression for about four years, and i always felt that there was something else going on. meds helped a little bit, but only to take the edge off the sadness. i was still having "emotional meltdowns" (which were essentially psychotic episodes) where i would just lose it - i'd either be in an almost uncontrollable rage, or completely inconsolable with crying, shaking and hyperventilating, etc. the thing that made it so difficult was that i couldn't identify the triggers, so i couldn't prepare for / avoid those situations. it was basically like there was a switch that flicked in my brain and suddenly i went into an "animalistic" (for lack of a better term) state that was based purely on instinct and emotion rather than logic. my mum even said once it was like i was possessed (lol thanks mum) but tbh it's kind of a good way to explain it - it was like i wasn't in control of my mind or body anymore. it could last a little while or up to an hour, but the worst part was that when i'd come out of it i'd have barely / no recollection of what happened. it's pretty scary to come to and have a whole period of time that you can't remember, and be told you did stuff you don't remember doing
i'm on mood stabilisers now (have been for about two years at this stage) so i don't get those crazy episodes anymore, but the rest of the bpd symptoms are still there. people talk about "black and white thinking" but with bpd it's like you have black and white emotions as well - it's all or nothing. i definitely used to have very unstable relationships - i would latch onto people immediately, and be terrified that they'd realise what a bad / broken person i was that i would constantly seek reassurance and attention from them. to a bpd it feels like a completely rational thing to do, but to a normal person receiving 5 text messages within ten minutes asking "are you mad at me" "sorry did i do something wrong omg i'm so sorry please don't hate me" "are you ignoring me what did i do" "i'm sorry i like you so much please don't leave me i didn't mean it" "please i need you don't leave me" is freaking terrifying, so invariably it pushes them away. i'm in a stable relationship now (he actually also has bpd which weirdly enough works?? we've been together over a year and a half and have never even had an argument, let alone split on each other) so i don't have that issue but the emotional instability is still a killer, especially once you start having to deal with adult stresses and responsibilities :')
when i was at my worst (in 2015) i was reeeeeally impulsive as well. i would binge and spend allllll my money, eat a tonne of food (or none at all), i was really promiscuous, got tattoos i really regret now, and self-harmed a lot.
um so basically that's my experience with bpd. i'm a lot better now, but i'm not gonna lie, it's still a struggle to cope. unfortunately bpd is really hard to treat (and some medical professionals flat-out refuse to diagnose you and/or treat you), and i know that it sucks feeling like you're adding something else onto the list of crap life's thrown at you, but if anything at least being aware of your symptoms and the way they effect you can help you prepare coping strategies and that kind of stuff.
not everyone with bpd responds to therapy, but DBT works best out of everything for borderline so take a look into that if you want! also idk if you're already on meds, but definitely ask about something that can maybe help stabilise your mood. unfortunately the reality with bpd is it can never be "cured" or go away, so it's about finding strategies to help you cope as best as you can day to day.
sorry for the essay (and sorry i couldn't end on a more positive note), but good luck!