Help with 7 month old kitten?

Hi. In November 08' I got a 6 week old kitten born sometime in October. He doesn't have any shots, as he is a strictly indoor cat. At first he constantly urinated in the kitchen on our linoleum floors but had shortly stopped when he was punished. Occasionally he pees in my room (I let him in there and he likes me more than my dad I think lol) and sometimes in the bathtub. Why is he peeing? It smells really bad and it takes forever to clean out the smell and air out the house. His litter box is sifted through admittedly every couple of days. He is a happy, super active kitty for his age, so I don't see why he would be peeing. Is it because he is starting to change and will start spraying soon? Please give me some insight. Thanks. :)