It started with a "migraine"; I'm learning to ignore them because they seem to follow a regular pattern of ten minutes or so of weird visual effects, and then they go away. No pain, just inconvenience because I can't do anything that requires me to be able to see fine detail during them. I can see well enough to move about past the flashing lights, so in this particular case I just carried on with what I was doing at the time, namely travelling to work.
But this migraine seemed to have a long tail of weird cognitive effects. Or perhaps the subsequent weirdness was completely unconnected, I don't know. Through the rest of the day I kept experiencing the sorts of sensations which normally lead me to identify that I'm in a dream rather than reality. Everything seemed vaguely familiar but slightly off, and I'm talking the lab where I've been working for 6 months now so it should be completely familiar. My short term memory felt like the memory of a dream; I couldn't fit together into coherent narrative the actions I'd been doing for the past half hour. I would be really surprised to see things that I'd put in a particular place ten minutes before, and the sight of them would remind me of a fragmented image of doing so rather than a normal memory of my doing that action, as if I'd done it in my sleep.
At one point I had an overwhelming sense of déjà vu, just couldn't shake the impression that I was reliving something that had happened before. Something completely banal, mind you, just having a cup of coffee with colleagues. I know that everybody has déjà vu sometimes, but this was much more intense and convincing than normal. Part of my brain was trying to reassure me that it was just a dream and all I had to do was wait to wake up, but in this case, unlike in any dream I can remember, I was absolutely certain that I was not dreaming. This disjunct scared me rather, and it took a lot of concentration not to panic. Obviously, being scared didn't help me to think clearly.
After a few hours my brain started interpreting the world normally again. It is most likely that this experience means absolutely nothing (sleep deprivation, maybe?), but I want to document it. Does anyone have any reassurance, (or reasons why I should be worried, I suppose)?