You know what this is literally like reading a page of what my brain goes through in a day lol. I have a serious issue with putting my phone away, it's just the best distraction from all the bad things in life that I'm experiencing atm. And when I've looked at a screen for literally more than 15 minutes I'll look up and get terrified at the sight of everything around me. I'll get dp and dr attacking me at the same time. The whole idea of me being here for no reason, everything happening randomly and people actually being able to see me terrifies me. It's like I'm stuck in my little consciousness in my head and everything around me is just this weird picture. This gives me 1000x claustrophobia at once, and it's like 30% of my day. Don't want to make this about me, just thought it'd be good to know you're not alone, I experience this so much.
But trust me this is for sure not a dementia disorder. For a while I thought I had gotten Alzheimer's because my granddad had it. But I would say that the possibility of someone getting that when your 17 is close to 0%. I truly believe you just have dpdr.
Now what I've done to reduce this feeling is honestly to stop thinking entirely. Lol it sounds weird but that's really the only thing that has helped me. And I don't just mean "don't think about it" because that just doesn't work. I mean full on turning off the brain for a minute or so. I don't think this will make any sense, but I've kind of learnt doing that since I got dpdr. My brain has an easier time shutting off when things get hard, and I have in some way learnt to control that, at least when I want to turn it on. I don't think this is a long term solution obviously, but it has helped me in the situations you describe. When I'm in that strong analysation of every existing thing I think to myself "you know what, stop thinking for a minute", then I'll do anything (like eat an apple or something haha), and when I come back my brain feels more ready to take on the day. Ugh idk if this tip makes any sense or if I just sounds crazy, but it's the only thing that's helped me. It's like I'm restarting my brain. On the other hand, I'm still struggling a lot with this. But I'm trying to survive somehow.
I know it's hard to feel normal because of quarantine. People always tell me to "interact more with people", but I also just live with my parents and they're pretty unbearable most times lol. So I don't really have an answer to that, I'm still having a hard time being with others because my brain keeps telling me no one's real even when I know they are.
I hope things work out for you tho. You'll eventually feel better and these feeling will start to fade, it's just going to take some work and time.
