How can I get my son to sleep through the night?

I can totally understand your situation. Well first of all, if you are a full time mum, as it seems like, make sure he is very active during the day and try keeping him awake (only one nap of 60-90 mins should be enough) during the day. Feed him well, am sure you giving him his purees and everything, then around 8.30 - 9 pm, give him some of your milk and off he shoud go to bed around 9.30. Believe me, he will be so tired that he will have to sleep the night off. My lil girl is on this routine and she wakes up around 10 am every morning. she's been doing this since she was 8 months old and she is going to be 1 year old in next week. It is a very very very bad idea to let him play at 4 am. remem he is the child, n you are in control, he has no idea what he is doing, but mummy u can change it all. if he is used to this treatment at this hour of the night, then he thinks that its completely normal, its play time and please please please don't put yourself in so much pain, do not leave your bed, this is the start of a disaster. if he wakes up, then do not feed him, a couple of time and he will know exactly that its time to sleep and remain in the cot, may be you could give him a cuddly toy to hang on to. I also completely disagree with the 'cry it out' solution. I believe in reuring the child to make him feel that you are always here for him and he is secure. do try the sleep at 9- 10 pm solution, it worked for me.