How can I bring up this flashback?

TW: CSA

Hey, so I already have a really tough time with being vulnerable with my T due to other developmental trauma and attachment issues.

But I had a somatic flashback that I want to tell him about. Basically the sensation is as graphic as you could get (sorry in advance for the next sentence). It was a penetration sensation inside my vagina and felt like two fingers spreading. It happened twice.

I want to say that in a way that is not going to leave me with the worst vulnerability hangover of my life. I also don’t want to be really embarrassed or sink into the floor while I say it out loud to a man.. Is there a more clinical way to say this? I know there’s value to him knowing about my experience but idk :( this just feels impossible to say at the moment.