My little easy child chews things like crazy. Shirt necklines, sleeves, the collar of his winter coat.
Strange as it sounds, one of the things that seems to have worked very well with Little easy child is to chew on a neoprene bathing cap. Durable fabric that he can't tear, not a choking hazard, and it seems to feel good in his mouth when it's wet. Sometimes he'll bundle the whole thing up and stuff it in his mouth, other times he'll just nibble on the corner.
Little easy child is a bit of a class clown and can often pass off the behaviour as just goofiness, so his friends don't tease him about the chewing. I do try to keep him away from smaller things that he can choke on.
Definitely sounds like Sensory Integration Disorder (SID), and I do agree with whoever suggested a neuropsychologist evaluation to look into this.
Incidentally, when I was a girl I used to soak washcloths in cold water and then chew on them until all the liquid was wrung out of them. As an adult, I have replaced chewing with brushing my teeth. A lot. For some reason it has the same effect, especially when I use baking soda instead of toothpaste. Don't know why the toothbrushing works, but it does, and I have a pretty good dose of Sensory Integration Disorder (SID) myself.
Trinity