I told my fiancé about my suspicions of CSA and I feel like a liar

Last night I had a bad flashback directly after sex and my poor fiancé had to witness it and felt terrible. He knows I have trauma from another incident but recently therapy and Spravato treatments have dug up nasty memories of being a toddler in my grandfathers house. I am almost positive that he abused me and also one of my cousins. I have no direct memory but I have a fuzzy memory of seeing him naked and I also had a lot of UTIs as a toddler. Anyway, while I was still really out of it last night I ended up disclosing my suspicions to my fiance, who was extremely supportive. But as soon as I told him I felt disgusting. Like I had lied, or like now that I had said it, now it was real. He keeps saying he wants to “investigate” it and get to the truth but I don’t think he understand there is nothing we can do. Grandpa is invited to the wedding this fall and fiancé has purposefully never met him. I’m worried interactions at the wedding won’t go well. Grandpa is notorious for making very inappropriate comments at me about sex and my body, I’m worried he will say something at the wedding and cause a scene. I just feel dirty and wrong and I don’t know what to do. I wish I had just shut up