If your baby is a term neonate with a weight of more than 2.5kg normally they finish the feed by 20mins.
Hence if the child is hungry ans still crying for a feed then probably the milk is insufficient.
The other method would be to measure urine output which has to be more than 7-8 times daily and stool output more than 6-8 times in a day if he is a newborn.
So top feed maybe necessary in your case if all the above is not happening.
Next Steps
Please try increasing your milk by taking normal diet with lots of liquids,fruits and veggies.
You can take lactate capsules 2capsules thrice a day for 10 days to increase lactation.