Toddles doesn't sleep

Hello lovelies,

I'm struggling. Does anyone else struggle with keeping your toddler asleep? Owen has been going to bed really well for a few months. I can lay him down and he sings himself to sleep. The last two nights, not so much. He screams till i lay with him. Its taken an hour both nights to get him asleep. Then hes awake by 4 am for the day and i can't get him back to sleep. We are talking no more than 8 hours of sleep each night. I know you might say, "its been 2 days, Jess. " But prior to 4 months ago, he didn't even sleep through the night yet and we had to CIO to get to this point. I just know this is going to be a rough set back. How do you keep your littles in bed and asleep at night?!