Is my baby getting enough?

Miriam
At first, my baby had trouble latching. I would pump and she would take about 4-5 ounces per feeding. 
Now, she's 3 1/2 weeks old and has learned to latch. She will nurse about every 2-3 hours until she falls asleep. 
My concern is that after she eats, she's so fussy! I pumped (after 3 hours) to see how much she's getting. Now I've been breastfeeding her, I've gone from getting 6 ounces every time to getting less than 3. 
Is my baby getting enough?