Hmm, I'm not sure if this is thrush or not (though the pain radiating through the breast was true for me when I had thrush), but as for the nipple turning purple - I experience vasospasms after feedings, so the nipple turns white and/or purple before returning to normal. Though, I can't imagine this is true for you as you've been breastfeeding for months and it's never happened before... Sorry I couldn't be more help!