Blacking out

I had something new happen and i wish to understand why, how and what purpose this serves.

I have only started venturing to the dating and sexual contact thing recently, i had no sexual experience when raped and have shied away since.

I am at a point where i don't as such run scared from my own demons, i will tackle them head on and have a bit of a "screw you" attitude to my own problems, my knee jerk reactions now is to do what makes me feel bad/scared and "force" myself to get over it, im sick of this stuff happening, so i force myself to power through things...but i need to understand reactions as well, i find educating myself on what's happening in my own brain is very helpful.

I had someone stay the weekend, sex was never on the cards and he knew that and it was not a problem, in the dark though one night he looked like the person who raped me, i kept telling myself to get the hell over it, stop being a dickface and calling myself a few choice names in my mind, he didn't know as i knee jerkly keep things to myself as well, even when at breakdown point.

At one point i blacked out, i lost consciousness for a few seconds, came too, happened again, had a wtf moment not knowing what was going on and it happened again, this has never happened before but i have not been confronted by someone who looked like him, in close proximity in the dark either, but even at other high stress points passing out has never happened.

After my crash and burn stage(which is the after math, i get exhausted, i can be stressed badly and not even know at the time, its the crash and burn when i realise) and i was able to piece memory back together, as my memory gets affected as well, it is only after crash and burn that bits of memory start coming back, but even then not all does...that i realised what happened.

Can anyone help me understand why, what went on in the brain, how does this even help me as i am sure this is some kind of useless protection method and how can i be stressed to the point of that happening and not even know it.