For the last month I have been sleeping for 12 hours straight not waking up or anything and it is a deep sleep where i wake up and look at the clock thinking to myself "there is no way i slept for that long". Even after sleeping for so long I find myself really tired and wanting to go back to bed. I am a night shift worker but do spend time outside regularly every day after I drag myself out of bed. I was recently tested to see if my thyroid was low and did not need to up my meds also i was tested for vit b-12 and alot of other things that may come cause my sleeping they all came back negitive. I have also tried the whole only sleep for 8 hours and wake myself up, but i was soo tired I would fall asleep while at work. What could be the problem with me?