Been so on the fence and don't know if I should trust and have confidence in myself

So I have been in a relationship for just under 6 years now, and for the past couple years maybe at the longest, I just have really been very on the fence and uncertain - but long story short, I just don't know if I should trust myself and my mind, and always doubt myself subsequently...

I always trust and have confidence and faith in my judgements and interpretations of things that happen in my relationship as they occur and are fresh, but almost literally always, second guess and doubt and question them and everything afterwards, later on when analyzing and thinking back on them. Which should I trust and have more confidence in? Afterwards I always just doubt and second guess myself, and feel like maybe I was just overreacting, or misinterpreting, or letting my emotions get the best of me in the moment sometimes, but like I said I almost always am just 99% positive and confident in my judgements and interpretations of things that happen in/shortly after the moment.

I'm always scared of course *after* the relationship has ended if it does, that I'll have some 'moment of clarity(s)' and realize/see (or just always have doubts in and question myself, regardless of anything) that I was the toxic one, the problem, and that I was just processing the information wrong you know...