I had thrush, which only manifested itself as the sharp shooting pains you describe and pains seemed to be deep in the boob, no sign of it in DD's mouth or any outward sign on my boob, the GP gave me a tablet Nilstat perhaps and some Daktarin gel for DD but said only had to use that if she showed signs, which she never did. I had read somewhere (maybe ABA book breastfeeding naturally) that thrush can present like that, so I went to GP suggesting thrush and she agreed, the Nilstat worked so I do think that is what it was. DD was maybe 2 months old at time.