If a 5-month-old baby is drinking less milk recently, it is important to remember that babies go through growth phases where they may need to adjust their sleeping and feeding habits. It is normal for babies to wake up during the night. If the baby is refusing to drink more than half of the usual amount, it is important to monitor their weight for any signs of decreased growth. If the baby has started solids, it may also affect their milk intake. If you have any other concerns or questions, don't hesitate to reach out to a healthcare professional for guidance.