Thanks again everyone. Around 7pm he threw up some yellow liquid with a tiny amount of fur in it. It was too small to even call it a hairball though. I was hoping that he'd be better after this episode. He later ate some dinner which was some canned food mixed with some dry. He didn't finish it all but he ate most of it and he was later trying to swallow a lot again. Maybe he has a sore throat. I tried looking up symptoms of sore throats in cats and it did say gagging and swallowing frequently are some which is what he's been doing. It also said that drooling, gulping, and reluctance to eat are symptoms too and a sore throat is a sign of an URI. He doesn't seem to have an URI though. I'm getting so frustrated by not knowing what's wrong with him and I hate having to watch him do the gag cough.