I am 12 years old, and I have a question. I get hard a lot, I'm getting hair under my arms, and I got a lot on my pubic area. When will my penis grow?
Your penis has been growing. It is nowhere near how small it was when you were a baby. It is during stage three, while you are having your growth spurt, that the penis grows in length the most. You can use the Tanner Stage Calculator to figure out what stage you are in. From your description you are probably close to your growth spurt.