My little girl was a lovely sleeper until 2 weeks ago. She slept in her crib for 4 hours consistently at night and several times up to 6 hours. She is now 6.5 weeks old and will wake up after 30 mins in the crib every time.You can set your watch by it, day or night. It doesn't matter if we put her  down deeply asleep or just sleepy, she has even self settled and slept for half an hour. We have tried every position, different blanket configurations, elevated head etc. She isn't hungry because she barely feeds when she wakes and will sleep fine in with me.