My baby is 19 weeks today and I have been waiting for this four month regression thing with sleep... it hasn't really reared its head! She has always been a great sleeper since two weeks old when she almost slept threw the night but I woke her up to breastfeed! Now she goes to bed at 10:30 and wakes up either at 2:30 or 5 am and then wakes up for good between 7:30 and 8! She rarely takes a nap during the day at least a long one it mainly consists of 20 min naps after each feeding!  Does every baby go through this sleep regression?? I also really didn't see much in the sounder week since she seemed ahead of the curve and was starting a lot of that stuff earlier so it felt more gradual then all of a sudden.