My pediatrician told me to nurse my baby every three hours. Does that mean from the start of a feeding or the end of one feeding to the next? Because his sessions sometimes last an hour.

Could mean from the start. But you know what, feed on demand. If your bub is not hungry, why force him to feed? A mum would need to schedule feeding if she has a newborn who's not feeding regularly - like mine when she was a newborn. She wouldn't feed every two hours, and so she wasn't pooping and peeing as frequently as newborns normally do. She just wanted to sleep and sleep, and hence, she lost more weight than she should have after the first week. I had to make sure to feed her every two hours, as per the pedia.

thanks