Coiled in the water dish then I would check for mites. He would be dead if he only weighted 100 grams at 3 years old. When they are hatched, they can weigh almost that. He should weight about 1000 grams at that age or more so he is still under weight. If he is housed with females then he probaly did breed to them to much! Good luck with them and I hope he becomes a big, fat, healthy adult!