Why Is My Room Specifically So Dusty??

It’s vacuumed, generally clean (aside from like, the occasional pile of clothes or the computer I still haven’t got a new desk for) but for some reason, my room always has this dusty smell to it.

I usually wouldn’t care too much, but my poor cat keeps sneezing. At first I thought maybe it was a health problem and planned to save up and take him to the vet. But, he has no other symptoms and it’s only in this room after an extended period of time. Like, 2-3 hours.

I keep my window open all day. I can’t find any physical dust anywhere. If it was pollen, I’d be sneezing too because I have bad hayfever.

What is happening and what can I do about it??