I am getting a painful blister (looks like an ulcer with a flat, white center) from my 18 month old. I'm not sure if his teeth are rubbing on my nipple or it's his latch, but it hurts like crazy. It eventually scabs over and heals, but I almost always get mastitis from it. This is my 16th time dealing with mastitis and I'm getting discouraged. I don't want to quit nursing until he's ready, but I am tired of getting sick. Anyone have any advice?