Hi, My son is 16.5 months old. We have been working with…

Hi,

My son is 16.5 months old. We have been working with 2 different sleep consultants for the past 2.5 months (first one had to take a leave of absence) and while they have helped our sleep situation, I am no longer using them, and we are still having serious issues getting him to bed at night.
Screaming for 20 mins- 1.5 hours sometimes. We tried the shuffle method at first, and that did not work. 3 nights at crib, then chair, then doorway etc. and it was too difficult for him having one of us in the room but not holding him. So, we would still have 2 hours of screaming with that. We then switched to Ferber method, 5, 10, 15. We had more success with that, but it was never "3 nights of crying and you're done". He would have a good night or two, then 3 night wakings with screaming like crazy. Or he would finally sleep through the night, but then 40 minutes of screaming before going to bed. Or go to bed great, and then up at 5:20am yelling.
What has seemed to work better for us lately, is putting him to sleep (this is of course after the exact same sleep routine every night-- play in room, lights dimmed, read 2-3 books, say goodnight to all of his animals, music bear on for 3 minutes and in crib, say goodnight and walk out) he stands up after we shut the door screaming. We learned that if we went back in within a minute or so, and picked him up and re-did the saying goodnight to his animals and spent another minute or two with him in our arms soothing him, that he'd go to bed easily without any crying. This was our method for the past 2 weeks, and he used to do this when he was an infant as well and I would breast feed him to sleep. If I layed him down and he screamed, I would pick up and let him nurse for another minute. Then I would lay him down again and he would be silent and go to sleep.
HOWEVER, past 3 nights, he has been screaming bloody murder even after our second go, and it has been 45-60 minutes of screaming. We have gone back to 5/10/15 and still the screaming.
Why do you think he has regressed? He was doing pretty well going to sleep especially for about a month -- with just a few minutes of fussing.
What would you recommend with this regression?
Specifically, tonight and last night, he will finally lay down, be silent for 6-10 minutes where I'll think he is asleep, and then he sits up and screams like crazy. Then he will lay back down because I don't go in, and repeat the same pattern.
I think he has finally exhausted himself by screaming now and is asleep, after 40 minutes.
Why after 2-3 months of training, is he still screaming so much? He was never a big cryer as a baby, and I was very conscious of not letting him scream and attending to him.
Do you have any recommendations for me? Thanks, Kim