hi my dd is 3 years old and she is constantly waking up through the night and not going back to sleep for about 4 hours she will wake up and just be in and out of her bed and be stood at her stair gaate no matter how many times i go put her back in her bed she will just not sleep any advice on how to get her sleeping through the night again as she use to sleep from 8pm till 10qm in the moring thanks xx