Sometimes these physical and emotional changes don't happen at the same time. A girl or boy can possibly mature emotionally before they do physically. The opposite is also true. This can be a very difficult time. Sometimes kids who start to develop early are not prepared for the myriad changes going on in their bodies.
Boys also feel that their bodies are out of proportion.
These feelings can make one very self-conscious. If you are going through these changes and finding it difficult, just remember that soon you will be a young man, a young woman. Talk to your parents about how you are feeling, or to a friend. Your friends are probably going through the same thing also and discussing the changes that are going on in your body won't make you feel strange. I know it might be hard to believe this, but your parents went through puberty too once.