I looked after a baby who cried from 5 months old when he started with me until just before he left at nearly a year old! The only thing that calmed him down was picking him up, he stopped immediately. His mum said she just left him to cry at home but I found that if I done that he just got worse and worse. This baby was carried in a sling a lot until coming to me for full time care so needed the close body contact. I didn't contemplate using a sling as it is not practical when you have 2 other under 2's to look after and as baby gets heavier it is not good for your back. You have to either grin and bear it and hope it improves or think about whether a constantly crying baby is fair on the other children in your care.