Unexplained Breast Growth at 47

For my 47th birthday my breasts went from 36A to 34D in a month. They are tender like I'm on my period all the time. I am not pregnant. I've had the hormone level & thyroid tests done and they all came back normal for a fertile female. I have not significantly changed in weight, in fact have lost 3 pounds last month and am 64" tall and 141 lbs (military so there's a bit of muscle in those numbers), and size 6. My periods are normal if not a little more frequent. I have only one ovary from a cyst removal 20 years ago but that has never affected fertility. Even weight gain 8 years ago did not do this to my breast size (I’ve recovered from the weight gain). My breasts have not lost any integrity of shape (no sagging here, not even close to considering the pencil test). A mammogram a year and a half ago came back normal. I have no lumps in the breasts or lymph nodes.

I'm told the hormone tests mean I'm NOT perimenopausal. I did have a tubal ligation a month before this happened and there has been no change in periods since then.

Any ideas on what it could be? I have an appointment with my GP at the end of the week but I understand she’s already scratching her head so I would love some possible avenues to consider or rule out.