I'm 4 days PP and my milk supply has started to come in. I've been breastfeeding my son every 2 to 3 hours but I supplement with formula because his blood sugar was low when he was born. He breastfeeds for about 10-15 minutes but then refuses to keep going. I feel like he isn't even getting any milk because I was able to give him formula right after and he drank the entire 2 ounces of formula. How can I be sure he's getting my breast milk? Should I just pump and feed?