It's all just pieces of the same experience of dp/dr, etc. Deja vu, Jamais vu, perception changes, things look "odd' or "off" somehow, appear as mirror images of themselves, etc....it's not that you 'HAVE' jamais vu (as if it was a disorder or something)... it's an Experience that comes during altered states of consciousness.
All those experiences are within the range of what any normal brain can "do" - but probably would only do it for a couple of seconds, then "re-center" the point of consciousness. With us, we stay in the Unreality state, or we keep re-entering it a hundred times a day.
Cynthia, you say it's the worst when you go in and out of some place. VERY common. That was always my worse experiences, too. The very concept of a "transition" - going in, or coming out of any actual place mimics the "transition" of going into or coming out of a state of consciousness. So it's more likely to produce "odd feelings of reality"
Same with the transitions of falling asleep and waking up. ANY transition is going to challenge the state of consciousness - and it's a very good example of precisely when you need to keep FOCUSING OUTWARD the hardest.
If you enter or leave a room and notice the transition is kicking the dp feelings up even higher, DO NOT try to "re-orient yourself" into feeling more normal. As soon as you TRY, you're making the entire experience a thousand times worse. The worse thing you can do is to try to MAKE things "seem familiar" - or to try to "feel right" ? the harder you try, the more elusive reality becomes. The more you TRY to make the room like it did five minutes ago, the more unusual it's going to become. Pick up a book, throw yourself into a conversation, count tiles on the floor, or do your nails or call someone to talk or balance your checkbook. Do ANYTHING NORMAL immediately - and that is still not going to make things feel normal, but at least you're not going to be making it worse.
Again, my metaphor of a ghost: if there are scary spirits trying to freak you out, and everytime you walk in the room and they say "boo!" and rattle their chains, if you get scared and start trying to find them or telling them to leave, they'll laugh and remember what a sucker you are and plan even more scary things for the next time. You are entertaining them. You are telling them that their tactics work on you.
If you give the scary noises NO attention, if you acknowledge to yourself "oh, boy....okay, this is that weird stuff that happens sometimes..." and the move ONWARD....push right past the "boo!" sounds and step over the chains and ignore all the pictures on the wall that are moving.........IMMERSE yourself in something in the moment that is NOT about the creepy feelings.
Those ghosts will say "well, shit. She's not falling for it." And they will eventually stop bothering you because it's not fun anymore.
This is not going to cure you in a day. Or a week. But it will cure you of these symptoms. The hardest thing you will ever do is to really DEDICATE yourselves to this, commit to it - and KEEP at it. It will cure you. Period. No if's and's or but's.
Yet........99 per cent of those who read this will not do it.