My son is two months old and he's developing the worst habit ever of sucking on his thumb. His dad thinks it's cute but I hate it. When his pacifier used to fall out of his mouth, he would just cry until we put it back in his mouth. But now if it falls out, he just replaces it with his thumb. When he's sleeping and I go to check on him his thumb is in his mouth. I know he's probably too young to get it, but is there anything I can do to stop this before it gets bad?