you probably need at least eight hours of sleep. what time do you need to get up? just go to bed eight hours or so before your wake up time! make small adjustments till your body adjust. if you wake up a little early, cool. never rush yourself in the morning. it often messes up your whole day...;-)
If you sleep 8 hours you will wake more tired then if you only sleep 7 and 1/2 hours. A sleep cycle is 1 and 1/2 hours long.... Sleep should be scheduled in those 1 and 1/2 hour intervals. ie... One and a half hours or three hours or four and a half hours or six hours or seven and a half hours or nine hours...etc etc. Waking in the middle of a sleep cycle will make it harder to wake and is not healthy for body or mind.