How soon will a routine be established?

Hi my baby is 3 weeks old. I thought i was all prepared for the arrival and knew what to expect but boy was i wrong!! what a shock to the system i feel my life has turned upside down! every day and night is so different some days she will feed 3-4 hrly and i feel we are getting somewhere and the last 2 days and nights she is taking less feed 2 hrly! can any one give me an idea of when a pattern or routine will appear ? i know every baby is different but tell me theres light at the end of this dark tunnel!:\?