Does anyone have any advice on sleep training a 21 month old who has already moved to a big boy bed.

He used to be such a good sleeper and would go through but Since the 18m sleep regression everything went downhill. He needs me to fall asleep so I lay there with him. If I don’t he’s so upset and just jumps off the bed and walks out. So he falls asleep and I leave and around 10pm or after he will wake and realise I’m not there and I’ll end up going back in and most of the time I’ll sleep in his room (double bed) as it’s just easier when your exhausted at 2am! If I put him back in bed he just gets back off and will cry until he’s sick.

Anyone else got a similar issue?