After lots of initial problems I've been happily bfing my ds for the past 11 months but just recently one nipple has got really sore and I don't know why or what to do about it. He already has his top 4 teeth and middle bottom 2 so teething seems unlikely as the cause. I don't think it's thrush because when I had that before my nipple went bubblegum pink - now it's more an angry red, but white just after a feed. Its worst when he latches on but its not great for the whole feed. Any ideas?