J.M.
I have family that went though this but my son still has a bink. He uses it only when he is upset and needs to calm down or when he is watching tv. Some children have blankets or stuffed animals that get chewed on. I think its similar to that, as in a bored/upset (anxious) habit but maybe he doesnt have the stuffy/bink/blanki to chew on so its his shirt. Its always available to him. It does make the shirt soaking wet and smelly and destroys it. Maybe try gum (my son loves gum but it needs to be a mint type so it doesnt taste like candy or he just swallows it) Or distracting him with something hands on to do. Clay is a good one because its very hands on and creative. You can even pound on it and its ok. You may consider talking to the doctor about it as well since they deal with LOTS of children. Good Luck, Jen
p.s. I myself have anxiety and I can tell you that yelling at him or punishing him is the worst thing you can do. He NEEDS to have an outlet and right now its chewing on his shirt, dont force him to change but offer other solutions and praise him for using them instead.