2 month old only drinking 20 oz per day!

For the last couple of days my 2 month old has gone from eating almost 4 ounces per feeding to only like 2-3 per feeding. I’ve been keeping track of her daily ounces and yesterday and today it’s been 20 oz.

She’s probably about 9 and a half pounds, we go to the doctor next Monday. She’s pooping and peeing regularly so I don’t understand why she slowed her eating??? She’s acting normal as well. Has anyone experienced this before with their baby?