Hiya. I'm sure it's nothing you've done wrong. They are all different. I used to rock my ds1 to sleep til I lost it at 6 months and did control crying which to be fair took one night and ten minutes. He went down better after that. Not sure that would work for you as its been 19 months. You might need to b gradual. Ds1 sleeps anything between half hour and two hours. He then sleeps between ten to 11 hours a night. Usually wakes once but either self settles or just needs his music. Bet I'm jinxing myself now!! Good luck.
Our DS is 19 months old, he is still sleeping in our bed with we didnt mind BUT he has started not to settle very well in our bed i think maybe he does need to go in his own room soon but i havent got a clue what his daytime naps should be? He has one for half and hour which is all i can get him to do whenever he feels like it, getting him to sleep is a nightmare. I carnt put him to sleep his dad has too.....i feel like i have done something wrong.