I suck my thumb in my sleep... how do I stop?!

I suck my thumb in my sleep... how do I stop?

I'm almost 13 and when I wake up my thumb is in my mouth...almost ALWAYS! I'm really scared that I won't be able to stop! Is this really bad? is it harmfull? How do I stop?

Please no rude comments, I'm really nervouse about this.

my sis used to suck her finger. right until she was about 10. it can be bad for u.if caused my sisters teeth to move, and she ended up getting braces... to try to make her stop, we first gave her something to use as comfort other than her finger. then.. lol... put a glove on. soon enough she latched onto the teddy, and forgot about the finger.
its just a comfort thing. some people have teddies or blankets, u and my sis have fingers and thumbs! my best friend still sucks her thumb on occasions and she is 21! if u wanna stop it try and find something else as comfort. perhaps thats all it needs?
or... just thought of something else. if that doesnt work... try that nail polish that tastes bad (to stop biting nails) and put it on ur thumb. the stuff is disguisting... but it stopped me biting my nails!
goodluck!