This is what I just read Hunter:
i remember reading about things like this in psychology... These cuts are self inflicted during sleep, that is if you defenitley didn't have them before you went to bed and just didn't notice...
It can be caused by a number of things; the most common being the following:
1. You were simply lying in an odd way during your sleep for a long period of time putting these marks on your body or rolling about it ur sleep your skin has scratched off the matress.
2. Your body becomes uncomfortable on the mattress your are sleeping on, become itchy for instance, so your brain autmatically reacts in your sleep by scratching, damaging the skin, in that way.
3. During a nightmare your brain struggles to differentiate sleep from conciousness and reacts in the real world to something going on in your sleep, for instance your getting chases by someone(the typical nightmare) and u get cornered, your body in the real world may automatically hold onto itself for protection out of confusion.
i hope this helps you understand why this might be happening!
Source(s): 1 year of psychology in high school, 1 year of psychology in university.