My kitty is sick

Monday his eye was leaking discharge and he was pawing at it. He looked better yesterday, but today his other eye looked even worse than the first one. So I took him to the vet and he’s lost three pounds! I can’t believe I haven’t noticed him not eating. I thought maybe he was getting thinner but it wasn’t super obvious. And he hadn’t been acting sick at all until today. Today he’s been very lethargic and when I put dinner out he ignored it and I haven’t seen him drink any water either. I’m worried for my kitty! The vet said he didn’t see any obvious reason for it. He took some blood and I’ll hear back on Friday. I’m so worried. I don’t understand how he got so sick so fast.
He’s not even climbing on my chest to sleep

he’s on the bed but at my feet.
Hopefully it’s nothing too serious.