Toddler sleep habits

Anyone else’s toddler (18mo or so) suddenly think 2:45-4:30/5am I play time? I don’t know where I went wrong! We have been trying to adjust his schedule since the change and omg, nightmare. Sometimes, it’s later in the morning. He went from 8pm bedtime, sleeping until 7:30am with bottle at 4:30am to 7:30 bedtime (now making him fall asleep on his own, it’s taking him 45 mins, typically) and sleeping until maybe 2:45-3:30 and up until 4:30/5!!!!! Something has got to give! It’s been a month and a half, and I’m clueless 🤯 we’ve tried helping to soothe back to sleep, to leaving him alone in the room. I just don’t know anymore!