You’re not alone — self-doubt nags every writer. I do get that it’s particularly imposing for you, though, as I’ve worked with writers suffering mental illnesses and they share their ups and downs with me. Notice I said “ups.” They struggle, but they also gain from writing—the joy of creation and self expression, an escape from the daily grind, and, yes, confidence. Their trick: stoking self-confidence by seeking visible improvement. Writing comes in many forms, so why not start small, with poems, essays, or short stories, and with things that don’t require research? Thus you reach “The End” quickly then can revise or start something new. Writers improve with every new draft and project. Seek out new techniques from writing books, take online courses since those don’t involve the social pressure of showing up in class. If money allows, hire a freelance editor to suggest improvements — but see it as suggestions, not criticism. You’ll see improvement and increase your confidence. Then tackle bigger projects if that’s your goal, saving submission for publication until your craft can compete.