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Try again to give him a bottle of his formula with the cereal in it. Sometimes babies will take it like this when they won't take it regularly. It's okay to put the cereal in the formula if you have a baby who is refusing a bottle.
I think that if he won't take it, there is a chance that he'll stop being hungry, and that's frightening. Sometimes you need to get something in his stomach so that he will try. Use an eye dropper and stroke his throat to get him to swallow.
Good luck, mom!