Hi all, our 20 months old has started waking in the middle of the night and won't go back to sleep! A few nights it's been 4:30/5am but last night it was 2:30 and he wouldn't go back to sleep at all- even with us in with him, he would lie in his cot but not sleep, and if we left him he would constantly cry and not give in. He's wide awake and asking to go downstairs. What do I do? Thanks :)