Help!

🌻🌺Trinkster🌺🌻 • Mamma to my little man 10/02/18 and little girl 11/29/19

My son is 15 weeks old. I recently went back to work, and he is home with his dad. He is eating 12-13 oz from 2pm to 11pm. I cant seem to keep up with pumping. I get around 8oz, 10 if I am lucky. Is it normal for him to be eating so much? He is a breastfed baby if that makes a difference.