Hi! Yeah, I too overthink to high heck myself. It's sorta in tandem with the ADHD for me, there really just hasn't been a single moment where I have had reprieve from my thoughts. Never a day where a single break in thought happened. Even at my worst during COVID when I was sick and endowed with brain fog, even when I was on meds that turned me into a zombie, even during the lulls. There was always that baseline thinking, that noise that kept on going.
In the past for me it was very noticeable, very distracting. Had my head in the clouds all the time, didn't matter to me much since I was ostracized from in school a lot but still. Overthinking and overactive imagination where I feel I am in the hyperfantasia catagory of thinker. Over time though I've gotten used to having it there, reminding me that I am me and still very much here. There's still a lot of problems that arise with it, but I've grown used to the constant stream of thought. To the point where I find the idea of having no thoughts to be genuinely terrifying at times. It has given me a lot to work with in my life, especially when it comes to writing fiction, worldbuilding, or journals; and artistry/drawing/painting. It's really good to have those outlets, cause at my worst, when I was in my peak depressive state, when I couldn't bring myself to do anything, that chatter in the skull turned inward and cannibalized on my sanity and ego. Questioning everything from my bonds, ties, and existence itself. Losing touch with myself and the people around me. Unable to separate the fear from interactions that never happened with people. A chaotic static noise fell over me that I'm still trying to pry myself free from. They got hands, but so do I. I'm very happy of the work I put in on taming the mind. I may be a chronic overthinker forever, to be frank I'd lose my mind if it were empty upstairs; but it is very possible to regain control of your mind.
I'm still early in my journey, I do find it really easy to slip into those patterns, the thought spirals that led me to here to begin with of existential dread, delusion, and self loathing. But with time, it can be overcome, tamed, and focused to be used for a force of positivity. In the past I called my mind a burden, and to an extent it can be; but I recognize just like any tool, it depends on how it's used. If the tool directs the user, then it's chaos. If the user guides the tool, then you can create anything.