I'm just so scared to do it. I've even considered secretly moving out and texting him later.. not sure what to do.
Tell him in person. He'll have a lot of questions and you'll have to provide answers. Make sure not to hint that there's a chance things will work out (as long as you're sure about your decision).
Breaking up doesn't directly lead to a happier situation. It just gives you more options. And choosing those options means going out of your comfort zone, which is probably why you're scared. It's not going to be easy, and the longer you don't do it, the harder it will be.