How many hours do you sleep?

So,I have to study for exams,and I get constantly tierd,cannot concentrate and feeling sleepy all the time,

My aunt says that I will never pass my exams in med school since I sleep 6,7-8hours,and that when she had studied for it she slept only 3-4hours,but I cannot do that,I just can't,I'm sooo tierd,and can't concentrate,during the day moustly,but during night it's better..

I go to sleep at 2 in the morning,and got up at 8

And she told me that I'm lazy and that I will never finish my med..

How many hours do you sleep usually,when you need to study for exams?