Hello everyone! Girls, who have babies sucking their thumb, it's okay with…

Hello everyone! Girls, who have babies sucking their thumb, it's okay with fingers, knuckles are fine, gums itch, but I noticed when he sleeps and it's time to feed him, his thumb in his mouth and then lies down, he deceives himself. How to stop it? They say this is a bad habit to suck on your thumb and affects the bite, we're almost four months old.