E.L.
I have a 20 month old who wakes up at 5 or 6 am and nurses and falls back to sleep. Even when he is half awake I put him back in his crib and he falls asleep until 830. Try putting him back in his crib. Ours did the same thing if I let him sleep with us- flailing around like a fish out of water. He didn't sleep as well in our bed and we slept horribly!