I'm almost 13 years old and my penis WILL NOT GROW but when I'm erect it grows HUGE and I have a whole bunch of pubic hair but no big penis size. I don't know what's wrong
There is nothing wrong with you and it sounds like you are developing just as you should be you are well into puberty and for being 12 that is normal and early than some boys your age.
Having a small penis when soft is also normal and getting pretty big when erect is normal as well.
The penis soft can be anywhere from an inch or maybe even less at your age and erect can range from a couple of inches to 5 or 6 for some boys.
It is also common for some guys to have a very small penis soft and become pretty large erect some guys are very large soft and when erect there is not a great deal of increase in size often called showers and growers. Just as people come in all sizes the same is true about the penis.
You have many years of growth and development ahead of you and your penis will definitely get bigger, everyone grows and develops at different rates and times and what the end result will is hard to predict along with how long the process will take.
For you and your age everything is normal and your growth and development is happening just the way it should be.