It could be lots of things, anything from a parasite to a tumour. Has it been over eating, or seemed hungrier than usual? If it as you say is eating anything it can, it could just be bloated. Is it visiting the loo as usual? If not then some part of it’s gastrointestinal tract could be blocked or have failed. If it seems happy so far then fingers crossed it’ll be ok, but if it goes lethargic like it’s sleeping, but isn’t then it’s not going to pull through. Fingers crossed for a positive outcome.  🤞🏻