Getting him milk and going to the couch only reinforces this behaviour. By now he has learned to wake up and have his nightly routine.Swaddling or Ferberizing at this age will not work. If this happened to any of my kids (I have a 4 and 1 yo's) I'd try the following. I'd move him to my room temporarily - put up a travel cot next to your bed (or get a mattress into his room). When he wakes in the night - I'd tell him to go to sleep, but won't pick him up. If you think he may be thirsty - give him a bit of water, NOT milk. I'd stroke him for a bit and lie back down. He will not like it, so initially there will be a lot of crying. I'd keep talking to him in a low voice and stroke him a bit, and if you have to pick him up - do it for only a brief moment - of course you don't want him to get hysterical and gag. I think the key here is to reassure him that you are there for him, but that he needs to learn to sooth himself. At 21 months he is old enough to self-sooth. Changing learned behaviour at this age is not easy but possible. This will not be easy and will take several difficult nights, but he'll need to learn that you mean business! So far he's learned that if he cries long/hard enough, he'll get his way. If you don't think that you can persevere, or that this is cruel - better not try. He may eventually grow out of it. I have a friend whose daughter woke up almost every night for over 3 years - when she woke up in the middle of the night she wanted a song and a story. My friend couldn't stand to hear her cry, so she just went along with it. Interestingly, when mom was away and grandparents were taking care of her - she miraculously slept through. Now she is 4.5 and I think sleeps better – she gets very tired at school and it helps.Good luck!