Just popping my nose in here for a second to offer up something that has helped me with some of this in case it could be of use to you.
That doubt anything even happened has always happened to me a lot, and over decades, with one of my assault experiences in particular. For me, I know that's about a few things, some of which are often at play for all sexual abuse or assault survivors: about the fact that I wasn't conscious for all of it in the first place, about how very young I was, about the way memory works when trauma occurs, about having it dismissed by police instead of being afforded the right to seek justice, about not being able to even talk about it at all with anyone for years, about how other abuse at the time being denied kind of made this abuse extra murky, and then about internalizing all the things we do from our culture that wants; that teaches us to do that us TO doubt ourselves.
One approach I found helped me most, and perhaps could help you, was that instead of trying to convince myself when those times cropped up, I learned to say to myself, "Okay, fine, but even if it did NOT happen, you still have these feelings (or these fears, or these trauma cues/triggers, whatever the thing at hand is), regardless, and you need to acknowledge and manage them regardless, so let's just move on and get to that."
In other words, I learned to be able to let go of a lot of attachment to proving my assault happened to myself and instead focus on caring for myself and healing regardless. Just tossing it out there in case it's something you want to try, too.