A.H.
Well not sure how old he is?? But most young kids don't have a strong sense of time and a schedule should only take a few days to adapt to if he is young. My kids use to be on a late schedule and when I accepted a FT job I had to get them on a routine. They were age 2 and 3. It took me a few days and wasn't bad at all.
I suggest making him wake up at a certain time at first maybe just a few hours earlier and move that up every day and put him down a bit earlier everyday. In my case my kids use to go to bed at 1030PM. So I started by putting them down at 9PM then 8PM but they adapted very well and really did not seem to notice. I know you are exhausted! I am also 7 mos pregnant! Them both being on a schedule is wonderful! THEy are now age 3 and 4.