No, that's not it. I'm not talking about nuances of meaning or words on the tip of your tongue, that's quite different.

The other day I was doing a crossword (I do a lot of them because I think they help a bit), and for me I'll either know an answer or not, or be sure that I should and struggle to think of it.

Anyway, I came across this one clue, and the answer to it (I forget now, nothing scary, just forgot) was something stupid like "garment". I absolutely knew the answer, I could visualise it, but I spent five minutes saying things to myself like: "gartion, gartive, garnament," and I got really scared because it was just gone. As if my vocabulary is a dictionary in my mind, and the entries just keep disappearing.

I don't know how to explain it any clearer. It's a new thing for me and definitely not normal.