Problem - I have pica I like eating mechanical pencil lead a lot I don't know why or how to tell?

So what's your question?

Pencil lead is made of clay and graphite, both common diet additives. The only problem is if you don't crush the lead thoroughly. You can get clay at any Asian grocery store, and activated charcoal at any health food store if you want the dietary benefits of those materials in safer forms.

There is no need to tell anybody anything. You might want to go to a library and ask the librarian to help you find some material on nutritional supplements.