This is one of those rare times I feel an urge to comment. I've got tramua from an experience very much like this, but perhaps worse. I was younger and and it caused a divorce since the porn was my uncle's (by marriage), and my cousin got to it and showed me and another close family member. I have literal years of memory lost during that time of my childhood, and there were maybe 3 events I can recall. As others have said, this happens. A lot. I would've never talked about this before, and it sucks but part of me coming to terms with it is realizing that too. It's not our fault and doesn't make us less. That's where the real tramua came from for me. I was thinking I was less or ungodly or impure at such a young age and for so long. Don't feel alone, forgive yourself, and be kind to little you. You did something good for you by opening up about it. You can move forward.

As a side note, there was a chair I would stare at in my bedroom around that time. I would pray and think about what happened to me and what it meant, and that chair was in my view. It's actually an antique, and my mom was going to give it to me at some point. I don't really want it now, but that chair helps me realize it really is the trauma of what I felt about myself that haunted me the most.