I was on lithum for 10 years before it started harming my kidneys to the point where I needed to come off it. I think that it did have some benefits when I was otherwise in an extreme bad mental health, but only in the sense that it muted the extreme emotions I might feel.
I originally went seeking help in my early twenties for what I now understand to be autistic meltdowns. When I would lose it, the consequences were devastating and I could not seem to figure out how to protect myself from them happening or from the blowback.
Psychiatry started by validating the suspected BPD as not exactly fitting type 1 or 2.. "Not-otherwise Specified" was the category I was given. When my pdoc left, the new one disqualified BPD and suggested "Generalized Anxiety with episodes of Acute Extreme Anxiety", I stuck with him until he retired. He eventually accepted my independently-sought assessment to ASD, as it was a much better fit for my life circumstances and also accounted for the challenges that I was seeing him for. He admitted he lacked the knowledge or background to qualify that himself or suggest it.
The medical system did not lead me where I needed to go, so I am glad that I did more on my own to get to where I am. Sorry to hear that your psychiatrist sucks.