Crying when I put her down...

IrishBride08

All of a sudden, my very good 5 month old sleeper is crying when I try to put her down in the crib for bed or a nap. 

At night it doesn't seem to happen when she first goes to sleep, but after she wakes up?  I still swaddle her. 

Any ideas? I've had to let her cry the last couple of nights and it breaks my heart cause she was never like this before!