Abdominal question/suggestions?

Hi guys. I am 6'1" 29.5in waist 153 pounds. 17 years old. I am so frustrated I've been weight lifting and exercising regularly 5 days a week. I've seen major results in my chest arms legs. But almost nothing in my abs. I have a 4 pack and can feel the 8 underneath but it's been that way for the past 3 months. I eat properly 6-8 times a day 300 calorie meals. I drink a gallon of water per day at least. It's not even a quarter inch of fat covering the last set of 4 at the bottom. I throw a half an hour of cardio in every other day before I lift. Idk what I'm doing wrong. I also drink a casein and whey protein mixture post workout. Any suggestions?