My 4 month old has stopped sleeping! Help!
I personally think that the 4 month sleep regression is the hardest part of the whole first year. Their sleep cycles change and they're more aware of their surroundings, and it all just falls apart.
Other typical regressions are 8-9 months (this coincided with pulling up for us) and when they switch from two naps to one (about 12 mos for us).
Baby-wearing for naps helped us a lot at this time. Is your crib sidecarred? It would be easier to deal with nightwakes than getting up and down, even in the same room.
I'm on my 3rd baby. The more I have, the more I think that sleep depends largely on development and temperament.