i was thinking pica, anxiety, or a sensory processing disorder. the third is more common than one might think, and can often explain other erratic behaviors as well.
You know, sometimes children start to chew/ eat non food items ( called pica) and its not psychological-- there are some medical causes for this ( I can't recall them right now, but I know that they exist.) If this is a habit he just picked up two weeks ago, even if it is an anxiety reaction -- something must have changed to make him do this-- either him or his environment. I bet the pediatrician will be able to tell you lots-- but are you going soon? I think this would qualify as a sick visit -- not something to wait on, you know?
On the running around, 4.5 year olds very commonly will get up and run around just to run -- seen it a million times-- so I would not worry about that part too much-- many parents of 4 year olds think that they have ADHD children-- but what they really have is 4 year olds -- just some thoughts there:)
He never sucked his thumb or anything like that. He also has these unusual spurts of energy - he will be sitting down, then all the sudden jump up and run through the house, scream and sit back down! I am concerned about ADHD, but am doing my research first as I don't want him to have to be put on meds.
Our son used to eat his shirts. He is adopted as well. He was diagnosed with an anxiety disorder. He is also ADHD. Does or did your son suck his thumb? Is he in therapy. A liscenced therapist could probably make some headway with him. It might be helpful to give him something designated to put in his mouth, such as a water bottle. Good luck and God bless.