How can it be possible to be so affected by something you can't remember happening?

I had an ex that I was hanging out with while we were dating, like freshly dating. After a night at the bar with some coworkers I had apparently blacked out. Which isn't possible because I only had 2 shots and a Heineken that I didn't even finish. We came to the conclusion that I was drugged somehow. At first I didn't think anything of it because supposedly his boss's wife also had it happen to her that same night. But to this day I don't know who would have had the chance to do something since I never leave my drink unattended. Only time I did was to go to the bathroom and he watched my drink for me. I don't recall leaving the bar or getting to a hotel and when I came to for about not even 30 seconds, he was on top of me. I passed back out so I hadn't completely come to. When I woke up finally I noticed I was wet. He told me I had gotten sick all over myself so he gave me a shower. Honestly I didn't know what to think so I chose to not think about it at all. Told myself were dating so whatever it couldn't be that bad..

Well we live in seperate states and I had decided I don't want anything to do with him but we didn't have hard feelings..

One day he was messaging me and I asked him how many times did we have sex that night and he said he doesn't remember, he just remembers we had sex a lot. I was not awake, coherent, or able to remember anything. I was so sick from whatever I had been drugged with that my father thought that I was still intoxicated the next morning when I got home and couldn't keep anything down he almost wanted to take me to the ER..

That's when it hit me.. It had to be him. He drugged me, and took advantage of me being unconscious. I know his boss'wife wasn't really drugged like I was and more likely just got really drunk as she was completely fine and remembers her night. Wasn't sick the next day or anything like me.

Lately I've been having reoccurring thoughts about it and it makes me just die inside. I could cry but how do you explain why you're crying about that... That whole night replays in my head. I start thinking about how I don't really know all of what happened to me or who else could have done things to me... I'm absolutely traumatized by the entire experience.

How does something you can't remember have such an impact like this? How can I start to move on?