It sounds like he could have a sore in his mouth either from an infection like herpes virus or calici virus or he may have something sharp stuck in his hard or soft palate or even thread wrapped around his tongue. He might have a tooth infection causing this too. This could even be from nausea as cats often drool when nauseous and that could be from hairballs if he is not getting hairball rememdy regularly.
Whatever it is this sounds like he is really feeling ill. I think you should see a vet with him as he is not eating or drinking. You should review how sick he seems to you and then decide if you want to see the emergency vet today or wait until your vet is open on Monday.
Hope this helps you!
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