The achy boob could also just be engorgement...I get mixed up about which boob I should feed from and sometimes do the same one a few times in a row (especially at night) and then a few days later I am all lopsided with one huge hard boob.

Yes breastfeeding is such guess work...I still don't know what I'm doing some days and I've been feeding for 2.5 yrs. My sil always said your baby has a relationship to your boobs that doesn't involve you (meaning your brain)... So I just always offer. Its hard because some babies will make themselves sick with milk, while others just refuse if they're not hungry...

Eventually they learn the art of sucking without drawing so much milk...