Why does my kitty do this?

I have an orange and white male cat. I got him when he was about 6 weeks old in October, these people were giving away free kittens in a carboard box so I couldn't resist. When he would lay on me and purr he would start to knead i guess with his paws. He would start to suck on my sleeve and it looked just like he was sucking from his mothers tit. He still does this occasionally. Its really cute when he does it but its also just weird. Does he do this because he was taken away from his mother too soon or does he think I'm his mom? I'm confused by it. Thanks for taking the time to read this:)