Puberty is a normal part of life in which your body changes physically. And in our culture, for girls it can often also come with expectations attached of a changing role in society, such as that of wife or mother. But you are still you, your goals and ambitions remain intact and you can still achieve your goals. Whatever dreams and ambitions you had before can still be achieved even though you are becoming a young lady and I would encourage you to feel able to express this.
Find friends or an adult you trust, such as your teacher, to assist you with attainting your goals. I can see you are concerned about this but be assured that nobody can stop you from achieving your dreams no matter what.