My DS is 15 mths old and constantly sucks his thumb. He sucks it quite hard and as well as sucking it when hes upset and to go to sleep, he also sucks it during the day. The problem is that its really red and sore with the skin breaking. I have no idea how to stop him, he does it so much that distraction isnt really an option. Has anyone an ideas on how to stop it at such a young age?