Snack feedings

Is anyone else struggling to get their baby to take a full bottle? I wish he would eat 6 ounces every 4 hours or something, but he eats 3-4 ounces every 2 hours. Sometimes 2 ounces here and there. He stopped taking 6-8 ounces before he goes to bed and he’s started waking up at night to try to eat. How can I fix this?