Responses
It's possible that you've added mangas ages ago but hardly ever updates until recently which makes you question if you've ever read this manga at all. Likewise, if the manga didn't leave a mark on you because it was plain, boring, typical etc. you're more likely to forget it. These sort of memory farts are normal and you shouldn't worry.
Ok. So if u go to my profile u will see I have a lot "want to read", "reading" and "already read" (maybe not as much as others..... But still) and due to that I get notification (of new chapters everyday) now........... I am not a person with good memory, so if I see a manga "for the first time in forever" I ask myself 'Am I really reading this?'........... And I must admit.......... I ask this question to myself EVERYDAY now........................ Is my memorial part of tge brain really that badΣ(  ̄□ ̄||)