If you wrote an autobiography you would be writing

a story about yourself.

Explanation:

Autobiography is the narrative of one person’s own life, written from their point of view. This is a non-fiction literary genre. While it is most often in a form of a book, it can also be made from personal writings put together, such as letters, diaries, and journals wrote during one's lifetime. However, an autobiography should always have at least part in which the narrator reviews their life from the current standpoint.

The difference between memoir and autobiography is usually that memories reflect more on the situation around the writer, society, politics, and other people, while an autobiography is simply the reflection of the writer on his or her life and work.