R.S.
My son did the same stuff around that age. It took me about two months to finally get him to stay in bed. It was AWFUL!! I tried everything and eventually had to resort so swatting his bum everytime he got out of bed. That was really hard for me since I reserve spanking for very severe situations. The worst part was that he was such an easy child except for this... I would not have resorted to the swatting except that our home was only marginally babyproof and I felt that it was a safety issue for him to be wandering the house while the adults were sleeping.