So our little girl will be 4 months on the 17th and she used to be really good about falling asleep. The last couple days she has been hysterically crying right before sleep and she will start to fall asleep then start crying again. This lasts maybe 10-15 min before she passes out. I should also state she is generally not a crier, she is a pretty happy baby that just gets a little fussy when upset. There is no fever, or tugging at ears, and she doesn't have the signs of reflux. Could this just be sleep regression or something else?