I Don't Understand Myself

(TW: Slight self-harm mentioned, no details)
Idk what's up but I think I have a personality issue. A lot of friends have mentioned I show a lot of signs of Borderline Personality Disorder and reading up on it, doesn't sound too far off. But I think there's more than that. Sometimes I feel like a different entity. Like I'm me, but I'm not me and I'm not in control. I can go from being my usual self to being the most hateful and crazy person in a split moment for literally no reason and it takes a while to go back to normal. I'd recently been in this latter state for roughly 13 hours or so until that has seemingly faded away for now. I tend to hurt myself a lil too when I'm like this. It feels unnatural, uncontrollable. I know in the past I've had arguments with whatever this side of me is. I don't know what's going on.
Whatever this is, I don't like it, but it seems to be out of my control. I'm not rushing to diagnose myself here, I just wanna try to figure out why my mind is doing what it's doing or am I maybe just crazy?

@DyersEve
Hi there. 💜 (Standard disclaimer that I'm just a random person on the internet with a keyboard who can't diagnose anything.)
The thing you're describing of feeling like you become a different person and things become really intense, emotionally volatile, etc. is something that could fit with BPD. It's possible for splitting episodes to last for hours/days.
https://uniquecs.co.uk/blog/bpd-splitting-episode-duration-and-effects/
There are also other psychological conditions that can involve identity fragmentation, like OSDD:
https://www.7cups.com/forum/trauma/DissociationRelatedDisorders_2335/OSDD1OSDD1aOSDD1bTheDifferences_263532/
It's also possible to have multiple conditions happening at once. There's a lot of overlap between different diagnoses send they all tend to have similar causes/conditions behind them (i.e. relational/attachment trauma), just manifesting in different ways.
Have you noticed any patterns as far as certain events or thoughts/feelings causing this different self to pop up?

@DyersEve
@jacek73 Rather unfortunately, I have in fact been seeing things that aren't there for around a decade and so sometimes hear voices that aren't there either.
Perhaps I should look for professional help at some point then...

@DyersEve
If this is the case (you didn't mention any visual or aural hallucinations in your earlier message) I think you shouldn't wait.
It is not a shame to get diagnosed. But that could be very dangerous for you, when you do nothing about the problem.
@jacek73 Here's the fun part: I still live at home with parents who aren't particularly big believers in therapy 🙃
Plan is to maybe move out by end of year though, so once I'm out, I'll look into it. But until then, it's off the table. But hey, that's why I'm here now, I guess.
I didn't mention the latter information in the original message as I felt it was unrelated to the main point I was talking about, but yeah those are an occasional problem too.
I just love my brain 💀