Over time, the tenderness does reduce. It could be how your baby is latching. My son sucked in his bottom lip and I had to always pull it out for the first weeks, otherwise it would kill!
Once you get a good rhythm going, you won't even notice your breasts filling up anymore. Your body will automatically know how much your baby needs and it will be there for them.
I meant my breast not breastfeeding, am in my fifth week.