Overthinking

Ever since I lost trust in my bf in the summer I continue till this day to overthink. It’s a nonstop thing and I always try to distract myself but it never works. The more I over think and think of the worse that’s the only thing I focus on. The thing is we have fixed things but I don’t feel like my mindset is fixed. I never will blame myself for overthinking though because what ever happened was never my fault. I stayed because I know the spark is still there.He is a good person but just with a bad mistake and I just see him as a bad person with that one mistake. I’ve talked to him about my overthinking and he tells me that I should distract myself or just not to overthink but he just doesn’t get it. He claims that he’s already been through that before but I’m talking about me. I just need need some ways to help myself.