Okay so I'm an 18 year old female. I still suck my thumb and recently I've been biting my thumb in my sleep. From what I know I've never done this before when I was younger. The bites sometimes leave blisters on my thumb or even small gashes and they sting for several days. Unfortunately my thumbsucking is a comfort mechanism soon have a hard time falling asleep without doing it. I don't know if it matters but I also have sleep apnea. Can anyone explain why I'm biting myself?