Bedtime with my 16 month old

Elizabeth
So for the past couple of months my son has been great at going to bed when we lay him down for bedtime. We follow a simple routine of kneeling in prayer, reading scriptures, and then he crawls up in his big boy bed and he goes to sleep to his little dog that plays lullabies. And he might whine a little but then falls straight to sleep. But now it takes him Forever and he cries the whole time. We have to be in his room by his bedside for him to fall asleep and I just can't take it any more. Any advice? Please!