Hi Trish, welcome! I also battle overthinking. My brain is like a race car that’s always like “go to go!” and I spend so many days trying to catch up with it, to have a handle on it. For a long time I used my addiction to numb it. As I’ve worked my sobriety I’ve found that there’s a legitimate cause - in my case, ADHD (just as present in adult people, including men and women, as it is in children; in women, it is greatly under diagnosed, because of social expectations about girls and women and how these don’t line up with stereotypes about ADHD behaviours) - and as I’ve learned about myself and my mind, I’ve found healthier ways to handle it. I use CBT techniques and EMDR stuff (I learned them from my counsellor).
Whatever it is that’s behind your mind, starting at it sober will help. There’s a good community here and lots of knowledgeable people (and useful threads like this, with books, podcasts, groups: Resources for our recovery) - you’re in the right space to learn 
Take care and never give up. You’re a good person and you deserve a safe, sober life where you can be your full self, not hidden behind booze, but instead walking your path, steady.