Waking up Late

I am now facing this problem of waking up late. I usually woke up six in the morning and do the chores but these past few days, I wake up 8 or 9. And when in the past I only get to sleep four hours, now, I sleep 8hours. This is not doing me good. Everytime I sleep more than 6 hours, it's making me weak and lazy the whole day. I think I should watch my eating habit and constant usage of computer. These might be the culprits.