Hi Hope
I see people have touched on therapy and medication (I have used both in my recovery), however the things that have helped me most with anxiety and overthinking, are meditation and exercise. I am trying to reintroduce the meditation into my daily schedule, but just starting it back up I find myself shutting up my own brain/anxiety much easier. The exersize (for me running and some weights) is an instant calm down and pick-me-up at the same time.
I wish you the best. One day at a time!