If he is not going through sleep regression or transition phases (big changes such as entering preschool, change of teachers, potty training, new sibling etc) which can cause night wakes, you can try enforcing sleep training on him to wean off milk and then helping him learn to self soothe back to sleep.
There r a few methods you can try out and can take a while to see results as he is an older baby by now - around 2 weeks. Have to stay consistent in the method you choose. You can read up more online.
aizahlahh