It could possible be your toothpaste. Some toothpaste contain sodium hydoxide which
with prolonged use could cause tissue to slough off.
Sorry that this help you a bit! Based on what you have been describing it is the only viable and safe option that I could come up with, and I am aware of some other possible options, but I do not make a definitive diagnosis over the internet . If you need a more precise diagnosis, that is something nobody can give you over the internet. If you are so concerned as I said in my last post, have it evaluated by your dentist or MD.
This did not help me the least bit! I know that i dont bite my cheek, this has went on for A LONG TIME! I think i would have come to that conclusion on my own if it were that simple.
I don't think you have anything to worry about. You are probably cheek biting. Have your dentist take a look at it.