Major update!
He has pancreatitis.
He's doing ok now though, he's on some meds, and we have to bring him to a different vet tomorrow and then he'll be there for 48 hours while they do xrays and stuff. He's also on IV right now.
They say he's gonna live! Yaaaay!
Reminds me of once when my dog had something, I forgot what, and while she had it, her eyes weren't focusing or anything, so she fell down the stairs, it was quite scary. Though her IV-patch did look silly in the end.