Why do i fall asleep in office and feel sleepy mostly? i usually takes 7 hours sleep but these days i'm getting up many times during sleep.

Fragmented sleep: You have a case of fragmented and non-restorative sleep disorder with excessive daytime sleepiness. It has multiple causes including primary or secondary etiology. Talk to a doctor who is familiar with sleep disorders and get a comprehensive physical exam and some basic blood screening to rule out physical and mental diseases. Otherwise, see a sleep medicine specialist and get a sleep study.