I am going to cross post this in the pregnant and nursing forum, because I have no idea if the two are related or not. Here it goes.
I am 9 weeks pregnant, just fyi. I have had nipple tenderness for a few weeks, but one side (my right) is getting really bad. Its actually behind the nipple, so that when I squeeze the areola (as if I were manually expressing milk), I get the absolute worst pain. It is getting to the point of being unbearable. I have what I would explain away as normal pregnancy nipple tenderness in the left breast, but when I do the manual expression "pose" with that breast, its not tender in the same spot. The pain has been getting worse every day. It is actually the worst when I get a let down until the milk is essentially gone, and then dd can suck all she wants with no pain at all, and when I do the compression, it doesn't hurt either. Also, it seems like that behind that nipple there is more mass...not a lot, but enough that its a bit noticeable. I have no symptoms other than the pain.
Also, my supply is almost gone in my left breast...it has always been lower, but its significanly lower now, to the point that dd will nurse on that through the tiny letdown and then want the right breast. I can tell by her swallowing that the letdown is not what it used to be...she used to suck-swallow and now its suck-suck-swallow. The right breast is suck-swallow, still.