I think that the changes to your "little guy" are some of the first that people notice. A lot of guys, myself included, talk about noticing a huge jump in growth within the first 3 weeks even. The sensations begin to change, too. As for feelings of "hardness", well the clitoris experiences "erections" just like the penis - and when it grows larger, due to T, it will naturally feel harder and more noticeable when you have an erection.