how to get him to sleep more

my 18 month old boy keeps waking up at 5:30am, which is way too early for me. he usually goes to bed between 8-9pm and sleeps through the night, but when he wakes up at 5:30 i cant get him to sleep more and i cant get enough sleep.

i did use ferbers method when he was 7 months old to stop night feedings and it work just fine, maxbe i should try that? any advice?

p.s. he sleeps in his crib but in room with us, cause of lack of space. we should be moving soon so i plan to put his crib in separate room.