Since you’re intent on writing a book, or have already written a book(s) you might no longer be just a writer, since your end goal is to write your own authentic work. You wouldn't be here if you haven't already done most of the work. So here’s how to tell what stage you are at:

A person becomes an author by creating an original written work, publishing it, then taking intellectual ownership of the content. The role involves more than just writing; it requires originating the ideas and content, and in a professional context like scientific publishing, it means contributing substantially to the work's conception, design, or critical review, and taking accountability for its accuracy.

Key aspects of being an author:
You originate content. As an author you conceive, develop and make the content available for others read, enjoy, use, by publishing in some form or other. The ideas and text, are yours alone, rather than copying someone else's work.

Key factors that make a person an author: 

• Original Creation: The individual must have originated the ideas, content, and stories in their work. Publish your work: The work is made public through publication, which can include books, articles, or even online essays and other forms of documentation.
• A Completed Work: This typically involves a finished piece of writing, such as a book, article, screenplay, or poem, as opposed to only having drafts or outlines. When you do that, you take intellectual ownership: Authorship involves taking intellectual responsibility for the work's content and integrity.
• Publication/Public Dissemination: The work needs to be shared with an audience beyond one's personal circle. This can range from traditional publishing and self-publishing a book to publishing articles, blog posts, a detailed fanfiction online or story, article, book published on Facebook.
• Accountability and Ownership: Authors usually own the copyright or intellectual property of their work and take public responsibility for its content and integrity. In a professional or academic context, this also includes being accountable for the accuracy of data and information presented. Professional criteria: In specific fields like academia, a formal set of criteria is often used, which requires substantial contributions to the work's conception or design, drafting or critically reviewing the work, and approving the final version.
• Authenticity and Voice: Many believe an author is defined by their authentic expression of their own thoughts and a unique voice, rather than just writing on assignment or as a ghostwriter (though the named person in a ghostwritten work is still legally considered the author). 
• Difference from a writer: While all authors are writers, not all writers are authors. The distinction often lies in the act of publishing and the ownership of the original ideas. When you get to that stage, you enter the official realm of the copywrite. This is a formal record that says you are the creator of the work and take full responsibility for the content or as per restrictions guidelines and rules as you determine for self protection. Normally when you publish a book with a traditional publisher, you use the services of a copywriter lawyer. This is serious stuff I'll cover in future chapter of how to Write Award Winning Fantasy. 

In essence, the transition from "writer" to "author" often occurs when the work is made public and the creator is formally credited as the originator of that specific, final piece of work.