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Nursing on clothes or other objects:
This behavior is most often displayed by a kitten or cat who was taken or weaned from his mother too early. Keep in mind that just like humans, cats are individuals too, and some may need more time with their mothers for emotional reasons, than others. This behavior often is one that the cat will outgrow as it gets older; however, some cats never seem to outgrow this special babyish behavior. The way to avoid your cat "nursing" on an item of clothing or household item you don’t want him to suck and chew on, is to put something on the item that is distasteful to your cat, such as paprika, hair spray, or citrus-smelling agents. This also works well with cats who like to chew on electric cords. Be aware though that chewing electric cords is often thought to be directly related to your cat’s anxiety due to being separated from you.

Why do cats knead?
This behavior is called "milk-treading." When you relax and sit quietly, you’re giving your cat the same signal he got from his mother when he was a kitten – that his mother was ready to let him suckle. A nursing kitten instinctively uses his paws to draw out the milk, gently pushing on his mother’s stomach to increase the milk flow. When older cats behave this way, it’s a good sign that they’re happy, content, and probably recalling their kitten hood.

Some cats who were taken away from their mother too early tend to do that, my cat does it. It just makes him feel safe, there’s nothing wrong with it and you should take it as a compliment (he thinks your his new mom )

My cat does the exact same thing, except he’ll do it anywhere, not just an arm. It’s fine, it generally means they’re happy ) My cat’s mom died when he was 3 weeks old though, so they had to bottle feed. But your cat is totally fine, as long as you can deal with the wetness of it all ))

Some cats do this their entire lives, especially if they were taken away from their mother before they were a full eight weeks old. You could mention it to the vet the next time you go but it is pretty normal behavior and isn’t worth a special trip to the vets. Take it as a complement that he thinks you’re his mom.

I have one kitten who just loves to "nurse" off of one of my fuzzy slippers. I affectionately refer to it as "looking for slipper nipples".

Many cats do this when they’re taken away from their mothers before being naturally weaned. It’s harmless, and will probably lessen with time (it doesn’t always, though). Plus, it does give you some good bonding time!

I had a tortiseshell kitty for 17 years who did the exact same thing. She licked and kneaded at her favorite people. She was also always trying to suck on my fingers until she was about 4 years old. After that she was content to just lick and knead and purr loudly. It was her way of being affectionate. I’m pretty sure she was taken from her mother too soon.

Anyway, you’re kitty’s fine. He just likes you a lot.