...you realize you have a plugged duct!
My LO is almost 15 months, and we've been nursing about 4 times a day for a little over a month since I pump weaned, and I thought maybe this kind of thing was behind us.
This time it turned out to be caused by a bleb, which I have never experienced before. It took me a while to even figure out what was going on, and then it was terrible trying to get rid of it. I'm a little worried about it just closing itself back up and coming back!
For moms who have had them - do they tend to be one-time things, or do I need to worry about the skin closing over the duct again?