At first glance this seems to be about the milk. I believe this is a red herring, and given the very small range of expression available to your very young child, demanding milk is the only way he has to communicate what he needs. If you step back and look at this from the perspective of developmental psychology, a different understanding is available.
It is essential that our children be bonded, connected and attached to their parents. This can be straightforward during the day, especially when they are young. Lots of time interacting during meals, playing, reading together etc. The tough part for very young children is at night time as sleep is a long time of separation. Imagine if during the day you left your young son alone for 8 hours. I suspect he would become very distressed and upset. With that image in mind, now take another look at what nighttime might be like from his perspective. It can be very scary for kids. And every child has a unique personality, with some better at handling this anxiety than others. Along with that, each child will have a different sense of attachment to their caring adults (i.e. parents) - and for some they have trouble holding on to that connection for the long duration that is 'nighttime'.
Let's get back to what you have described, this time adding in the notion that nighttime is along time to be away from Mommy or Daddy: Your son has awoken in the middle of the night, realizes he is separated from you, and does the only thing he can think of to get close to you and comfort himself and (as you have put it) demands milk.
Does that make sense? The first step is to make sense of the behaviour, to fully understand and know your son. If you feel this interpretation resonates, that it makes sense then you can start on the journey to making him feel better.
If you think this applies to your situation, or you are curious, then my advice would be to do the following:
- spend more time just prior to bedtime giving your son lots of love and attention
- take your time at bedtime - I know how busy life is and how exhausting parenting a toddler can be and many, many times all you want is a break BUT if you rush through bedtime you will only be setting the stage for the separation anxiety
- acknowledge what your son may be feeling but cannot express - that it is hard to say goodbye and close his eyes and use your words to let him know that your heart is connected to his even while he sleeps, that you will see him in your dreams
Then when he does wake up - instead of reaching for the bottle of milk, reach for your soothing voice and presence. Acknowledge his fears, work on ways to give him some piece of you to hang onto until morning, reassure him that he is loved and safe.
This will not result in a magical cure... it can take a long time, of consistently working on your attachment and connection. It is worth it in the end, both for your piece of mind and for your sons well being.
Tips to stay close when apart:
- smells are important! give your child something that smells like you -- used pillow case, something you have slept in
- bridge the gap between bedtime and morning with your words -- e.g. "I'll smother you in kisses when you wake in the morning and during the night I will be watching over you in your dreams"
- read The Invisible String book together and use that to reinforce that your heart is connected to your sons by a string that he can pull on anytime to feel you close to him
One last thing - sorry this is so long!
Imagine your son has a cup of Momma Love (or Daddy love, etc) and when he feels that cup is full to overflowing then he is able to be brave, strong, free, calm BUT when the cup feels empty he is lost and he will feel his very survival requires your immediate physical proximity and full attention - almost as much as he needs air to breath!
Now think of all the ways in which you can fill up his cup. Every child is different and every parent is different, so you will need to think about what works for you, but keep in mind that cup. For my child, I've noticed the cup is full when we have spent a lot of physical time together and also when she is well rested, well fed, healthy. These are many ways to fill the cup! When my daughter knows, truly believes, she is important to me and special just the way she is, her cup is full. Life is always going to through things at our kids - they will have to be resilient and things will not always go the way they want, but if their cup is full, or nearly full, they will be able to do anything. Your job is to keep your sons cup as full as you can, and acknowledge that if the cup gets empty, he will need more of you, rely more upon you. This is natural and should be expected. There will be an ebb and a flow. And as he matures, you can teach him how to fill his own cup, so he can be self-reliant.
One last thing, this article may help you feel you are not alone and give you hope: https://neufeldinstitute.org/bed-time-struggles/