I am 17 and my breasts have been growing extremely slow over the past 2-3 years. (I saw my first period at 15). I believe I have reached a small B cup but I can’t determine it yet (as the model of 32B bralette I bought is not filled on the outside parts). I was an A cup for the last 2 years but I can say that I was filling it more and more over the years (at the beginning my breasts looked emptier, now they are a bit fuller and rounder but I still feel like they are empty). I have a weird question about my breast growth. The inside parts are flat but on the outside my breasts are fuller. When I am sleeping, I lay on my chest. I am not sure if that causes a problem in their growth but is that the reason they grow in that state?

My sister has grown as much breast as I got now (from A cup to B cup) in just 1 year and she is 14 (she saw her first period at 12-13 (can’t remember 😂). So... I wonder. Are my breasts going through certain stages one by one? I don’t know exactly but I guess for example, first the middle, then the outside parts, then the top part and the inside part? Or should they grow all together?