Usually once the reach adult size their shedding slows down. My boy who is over two years only sheds once every 3-4 months. Also, you could've gotten him right after he finished a shed and still had a long way to go until the next one. Usually, they turn a little grayish a few days before a shed, and then they turn into snowmen. I haven't heard of a chameleon just, not shedding, but I wouldn't worry about it too much until 6 months goes by without a shed. Make sure your humidity is at the proper levels and you should be fine.