sleep deprivation

I've only had this app for a couple of days but have been tracking my six week olds sleep to see if there is a pattern - there isn't. She seems to sleep better during the day and at night - the pediatrician made some suggestions and I've done lots of reading - when and how to you start a routine? When she's sleeping she will not wake up for anything!! I'm concerned because I will be going back to work soon. I've been trying to do the 'sleep when they sleep' easier said than done!!!