How my sister explained it "welcome to womanhood" lol. Seriously the tenderness will continue as long as your on estrogen and T blockers, This is normal. This is called budding, which all girls go thru during puberty. The breast tissue is growing, causing the skin to itch and stretch just around the areola, and be very sensitive. Even just a slight bump can hurt. After a few months it will start to get hard like a lump just behind the nipple area, making the nipple start to protrude. The protruding nipple I had the hardest time with, getting very stimulated by the constant rubbing of a shirt, hence the need for training bras in natal gals. Everything should calm down sensitivity wise soon and breast tissue keeps getting fuller and fuller. For me now they have grown to a full C cup and a full Dwith breast augmentation. Depending on your genetics will determine your size. Look at your sisters and mother for a size you'll be close to, which was pretty accurate for me anyways.