You may have what is called ...
a trained night crier.
If you rock the baby to sleep and then put it down for the night, it never learns to put itself back to sleep. It took only a week, for us to get our lil crumb snatcher to sleep from 8 PM till 7 AM w/ the usual afternoon nap included.
Good Luck and great Blessings on the wee one.
http://www.med.umich.edu/1libr/pa/pa_nightcr_hhg.htm