Why won't my kitten(3 months) stop kneading his paws?

I have 3 cats, they all knead their paws. It's normal. It's to get used to a change. Cats usually knead their paws before they lay on something, to makes sure that the item they are about to lay on is safe. Your cat will probably do this all his life, as my 13 year old cat does. He probably purrs a lot to either show that he likes something, or is nervous about things happening around him. There is no need to worry, it is a cat's nature. You should probably start to worry if he isn't doing this every once in a while. But to summarize, kneading and purring a lot is normal, and almost expected. You and your cat are fine. (: