I chew the inside of my mouth. I not always do that when stressed, it is also a bad habit I do when not stressed. I am actually doing it right now (stopped after typing this) and it was not started because I was stressed. Sometimes I do it for so long that it hurts for up for a few days (the last time i did that was last week). I can go for a long time without doing it and then here I am again doing it.