I Feel Like I'm Losing My Mind

I can’t get it out of my head, him with her..... what happened the full details because I feel he didn’t fully tell me it all. I can’t move on, I love him I want to be with him but idk how to move on. How to remove this from my memory, how to feel sane.
I can’t sleep; I have nightmares.. I wake up depressed, go to sleep depressed. I want to feel numb every second because this pain is unbearable, these images are unforgivable.