Has my brain collapsed during quarantine or is my OCD playing tricks on me? I feel like I'm getting dementia in my 20s. Could I have ADHD (always suspected having it) or something worse?

I was asked for my date of birth today and it took me literal seconds to process the answer. Happens way too often lately with simple questions. You could ask me what year it is and I'd have to take a second to think about it (don't think it's related to my memory).
It's not just slow processing speed but like my mind completely stops at times. It feels like I'm living my routine doing everything mechanically and anything that requires thinking makes me crash.

It's like my brain blanks out sometimes. I also always seem to be distracted thinking about something that happened previously. Hard to describe. Like I'm constantly zoned out and I have to snap-in to reality to form an active thought.