You really need to get him to a vet. Cats not eating is actually quite harmful for them as it causes fatty liver syndrome. With the inappetance, behavioral changes, and apparent discomfort it is definitely something that will require medical attention.
Hope he's well soon!
"He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion."