Some of the things you have mentioned seem to be due to anxiety. The overthinking is what we refer to as rumination. The best way to deal with anxiety would be a combination of medication , therapy , lifestyle changes like exercise, yoga and mindfulness . You should also get your
thyroid levels checked to make sure that there is no issue there. For mindfulness meditation there are several free apps available which allow you to practice mindfulness from home- you can try something like the simple habit app. Please also visit a therapist who can help you learn methods to deal with the anxiety.