My 15 month old son was an excellent sleeper right up till he was 11 months. I could put him down awake and he would just go to sleep but things changed almost overnight and are getting worse and worse. He wakes up approx 2am every night and just will not go back to sleep unless I take him into our bed where he drops straight back off. If I leave him in his cot he just becomes hysterical. I have tried sneaking him back in once I believe he is asleep but the minute I put him down he wakes up screaming. Any advice would be apprieciated.