To me it feels like when you are thinking of a word or thing but seem to be stuck. Or when you realize something, suspect something but can't put your finger on it. And when you just had the word or phrase in mind but then you forget it and it was at the tip of your tongue.
This is how DP feels for me. Looking at my environment, I recognize everything but it's as if something is off and I can't...put my finger on it. It's like some invisible veil or cloak separating me from the outside world. Everything seems questionable, objects look dull, like they lost some dimensional aspect to them.
Things are 3-d for me, i have great spatial awareness but everything seems like if my perception is congested, blocked from breathing in the whole liveliness of things.
Interesting you point out you have ADHD, you might wanna address that. While there is not a strong argument between the link of ADHD and DP, there are a few concomitants that follow ADHD.
Add/ADHD individuals almost always suffer from some form of memory problem, cognitive problems.