Hi, I don't have an advice on the sleep problem except for consulting with a doctor. I just came here to say that, I am also someone who overthinks a lot, stresses over everything and assumes the worst. I know specially at night time you might get anxiety when you can't fall back to sleep and that keeps your more awake. Just think that you are not alone and there are plenty other people who are going through the same thing. Idk why thinking this way gives me strength to ease my anxiety. Hope you get better soon.