I'm sure you can be helped. You don't mention having seen a proper specialist psychiatrist or psychologist for a thorough assessment and a proper diagnosis, and planning treatment without that, can waste a lot of time. Over-thinking can be related to depression, or more likely to OCD, a form of Obsessive-Compulsive Disorder. In that case, some antidepressants can reduce the force of OCD, and CBT would probably be technique you could try which is best backed by good research evidence. It is uncommon for it not to work, though sometimes, for different reasons, individuals feel resistant to the process, and don't really want to accept the work it involves.
I hope you are otherwise leading a busy life, as rather than "distraction" as an empty technique, keeping oneself focused on work, hobbies, interactions with other people, and so on, can make it far harder for the overthinking habit to get and keep a grip.
You might find Mindfulness enjoyable and it may suit you. Personally I worry that it has become too much of a fashionable fad ; and some obsessive people like yourself find it hard to take to as they are reluctant to relax and let go of the obsessive thoughts. But try it, and feel free to return to the forum and let us know how it went, in your experience.
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