Kitten Sucks on His Stomach?

My kitten Brody is 6 months old now. Whenever it's time to lay on my lap, he curls up and begins to suck on his stomach, begins kneading my leg, and purring very loudly. He does the same thing at night when we go to bed, he'll lay on the pillow above my head and do the same thing except he kneads my head or the pillow.

That's the only time he does it, he doesn't do it when he's laying on the chairs by himself and sleeping. So I'm wondering if he was too young when I got him? He was 8 weeks old, and since I've had him I've had him neutered and he's had all his shots. He's very happy and playful, loving and healthy.

By Terry R. from Kent, WA