I don't know whether to take from your post that you are trying to stay awake solidly from midnight to 6am? This isn't the way it should be!
I think looking at the bigger picture here would be more helpful than your specific body clock question.
If you get your baby feeding well and sleeping well over 24 hours a day, then night feeds can reasonably reduce to maybe 3 or four per night at most.
I suspect you have a baby that is neither feeding well nor is she sleeping well enough in the daytime. Solving daytime problems often results in easier night times and daytime problems are easier to deal with because you are awake.
For the first 6 weeks (so now for your baby) your daytimes should consist of: If baby is not feeding he should be asleep or trying to get to sleep.
Get a bouncy chair with a removable arch and remove the arch. Feed baby fully - at least two 'sides' if breastfeeding. Then wind him for 10 minutes then into bouncy chair (which holds baby in a good position for colic/reflux). You sit on the sofa and bounce and bounce and bounce that chair until baby is asleep.
90 minutes after first starting to feed, stop bouncing and wait for baby to wake up. The repeat the whole process starting with a feed, wind, bounce, sleep - every 90 minutes.
Once you have established regular sleep and feeding through the daytime, it should then hopefully improve your night times significantly.
I would also recommend introducing a dummy within the next few weeks.