My son is going to be 3 in 6 days now. He keeps biting and chewing everything he finds in the house. He seems to have not developed the difference between edible and non edible as of now. Is this normal. He will not swallow anything though, be that toys or a piece of cloth, a rubber band, everything you can imagine in a household, has to go inside his mouth. He has this habit of sucking his thumb too. Plz suggest a remedy, and also is this normal for a 3 year old