[nwyori]

Hi ahpuuro,

There are a few potential reasons for the temporary shrinkage, you will just need to test it out!

Is your BCP mixed or progestin only?
Have you been gradually building up the dosage of BO, and have you experienced estrogen dominance symptoms (spotting, weight gain, etc)?
Do you cycle BO with milk thistle or dandelion root?
What's your diet like?

I had the same issues when I first started PM (boobs shrinking in luteal when they are supposed to be at their fullest), and I think it's because the estrogen receptors were desensitized by a huge influx of E, or because the ratio between progesterone and estrogen was not ideal. 

I also noticed that since I started NBE, fullness appears right after my period (follicular), not before it as it used to be. My hypothesis is that a high estrogen level is ideal for the follicular phase, but in luteal it's too high in comparison to progesterone, and that inhibits growth. 

Hope that helps a bit and happy growth!!