My daughter has suddenly done the same thing- she needs/wants us to stay in the room until she falls asleep... she is 14 months. Prior to this she was a good sleeper and was able to fall asleep on her own and was ok with us putting her in the crib awake - and then it all changed
It is so hard to figure out what is going on because there are so many possible factors - just getting over being ill, couple trips away, teething - molars i think, development, separation anxiety, over tired because the naps have been messed up too and we have just recently switched to 1 nap, - you just never know what is going on - it seems there are always so many factors....
Our daughter is very spirited and can be extreme when she gets upset... she often just gets madder with any intervention or help from us but yet is just struggling herself... anyway i am rambling... the point to the story is i came across the wi/wo method and tried it yesterday - 20 minutes of major screaming and then she went to sleep
todays naps were better already too
and i will definately do the wi/wo again tonight...
I found for me it was better to pop my head in the door instead of walking all the way in (she seemed to get madder when i left) and to just tell her to lie down and that it was time for sleepy and close the door... i only went in if she didn't lie down on her own then i would go in and help her lie down and leave. Got to the point that all i would have to do is open the door and she would lie down and quiet. you could tell there were times she was ok but yelled just to check if i was still there and was going to peek in on her - i think that assured her that she wasn't alone and helped the separation anxiety part of it.
anyway - i tried it, i was a little skeptical, but it worked. i will continue.. let me know if you try it and how it goes for you... Good luck!