Self-doubts are normal! I feel fairly certain that all authors must go through periods when they are uncertain of their abilities and possibilities. If you have a passion for writing, do not deny it! The more that you write, the more proficient you will become. Writing is your "true thing" if it's what you love to do! I've written three self-published novels of Atlantis -- self-published because I doubt my ability to sell them for "legitimate" publication, but I do love to write and felt compelled to produce those stories, longed to have them published. So, my advice to you is to keep writing and also reading, expand your horizons, hone your abilities! Good luck!