Your baby should have been gradually gaining back any weight loss from the first 4 days, until they were back to birthweight at 2 weeks old. Breastfeeding should not be painful for you. Your baby comes to the breast and feedings are comfortable for you. You should not be experiencing any breast pain or nipple pain. When your baby is breastfeeding he should be relaxing at breast, focused on feeding, staying put and not coming on and off, multiple times during the feeding. Your baby should be feeding about 8 times a day. Perhaps it is 7 or perhaps it is 9 somewhere in there would be normal.
