Hi
You are most likely suffering from hypersomnia, an excessive sleep condition where a person sleeps for 10 or more hours each night (for at least two consecutive weeks) and still experiences feelings of tiredness during the day. It may present as excessive daytime sleepiness or nocturnal sleep of long duration (as much as 12 h or more) or sleep drunkenness. Patients do not get abnormal amounts of night sleep rather they have problems waking up in the morning and staying awake during the day.
The causes can be genetic, brain damage or medical disorders such as clinical depression, uremia and fibromyalgia. Sometimes hypersomnia may be other sleep disorders such as narcolepsy, sleep apnea, and restless leg syndrome. Hypersomnia is sometimes misdiagnosed as narcolepsy where a person experiences a sudden onset of sleepiness.
You should consult a psychologist for a complete medical and psychological workup to rule out any other illnesses. He may then prescribe you some anti-depressants and advise psychotherapy to overcome your negative thinking patterns. Besides you should adopt other measures like avoiding caffeine and alcohol, exercising regularly, using some relaxation techniques and perhaps putting your thoughts on paper, so that you stress is relieved.
Do keep us posted about your progress. Take care
Research Restless Leg Syndrome and Periodic Limb Movement Disorder and see if these are something you need to discuss with your doctor.
Feeling the need for excessive sleep can be due to the sleep one is getting not being restorative due to frequent sleep stage disruptions. If medical tests for other things that can cause excessive tiredness are normal, a sleep study could determine if a sleep disorder is the culprit.