What does it mean that i'm always feel sleepy even i have enough sleep during at night time from 11pm to 6am then got in work at 9:30am i feel sleepy.

Many possibilities : You should see a sleep physician if you're not feeling depressed. Otherwise see your family doctor for treatment or referrals. Things to rule out are sleep apnea, narcolepsy, idiopathic central nervous system hypersomnia, periodic. Limb movements of sleep, circadian rhythm sleep disorder, hypothyroidism , anemia, and uterine fibroids, and medication effects. Best wishes to you!