Baby Not Drinking

Kortni
I'm at a loss on what to do here. My son is almost 9 months old and decided to start refusing nursing last Tuesday. It's been a week now of pumping and I don't know how much more I can take. I'm not able to pump more than a couple ounces at a time. And he has been refusing milk out of a sippy cup unless it's bed time. This past week he's had maybe 20 oz of milk total. Any ideas on how to get him to eat?