oh Lordy I remember this
Horrific.
I can’t offer any solutions at all because everything I tried failed. (All of the above suggestions, black out curtains, silence,stay in the room, shorter nap in the day, moving bed times, snack before bed in case it was hunger waking him, no stimulation etc etc etc)
So I just had to ride the storm.
Ended up downstairs with a blanket on one sofa and let him do his thing.
Accepted that this child just DID NOT SLEEP so neither did I for the first 5 years of his life.
Has yours previously been a good sleeper? Is this sleep thing a new thing?
Mine never was so it was the norm for us. Averaged 3-4 hours unbroken sleep every night.
Adapt your sleep to make up for it. I used to go to bed as soon as he was asleep.
We would take shifts so one or the other of us could have a lie in on a day off, or dh would take him out for a couple of hours at weekends so I could get into bed and sleep in peace in the day. (Unless postie knocked, or people popped round or neighbours were noisy as fuck)
Sympathies though, it is extremely challenging.