Re lactation?

So my son will be 2 in December my breast milk has been fully dried up for about a year and I’ve checked it from time to time just to make sure nothing comes out.. anyways yesterday I noticed my breast were a little tender towards my armpit where my milk glands would be and I decided to check and sure enough I’m lactating again. I’m 2 weeks away from a period so I’m not sure of anything but does anyone know why this could happen or has it happened to you? I don’t know why I’m randomly starting to reproduce milk.