I had this with dd#2.went from lovely sleeper to child from :twisted: .
After lots of advise from BW we came up with solution.
Lay down ds.Go out of the room,shut the door,count to 10.Go back in lay him down,go out and shut the door.Count to 10.Go in lay him down etc.etc.
You really have to persevere with this as the first few nights are a nightmare.The screaming will drive you mad.I always do my stomach twists or pelvic floors or bum clenches to the count of 10.I now only have to do this if she is soooo overtired and hasn't had a nap all day.
I'm only just starting this on the naps as I wanted to crack the night time first.I also do this if she wakes during the night.
Also at 12 months check the teeth and ears first in case he needs paracetamol.(I forgot that at first :oops: she was in agony for a while as I was so caught up in the whole crying thing)
Good luck.