[noodlez]

I déveloped my fibroadenoma shortly after starting bc. My mom has one too which she got around the same age as I am now for the same reason. It's not something to worry about if it is but I would go to the doctor to rule anything out.
In short, birth control can definitely effect the growth of the glands and nodules within your breasts.

I believe they say day five because it is the most neutral day for hormone fluctuation within your cycle. This would also explain the birth control theory. Contribution theory as day five is a sugar pill day