How fast can someone with PTSD block out a memory?

I have PTSD and i cannot remember chunks of my past (and much of what i can remember is traumatic). Sometimes i have nightmares about being raped, but i can't tell if it is just a metaphor for the powerlessness i felt or actual or memories bleeding through. It is hard not being able to trust my memories because i don't know the extent of the abuse or if what i am repressing keeps me oblivious to dangerous people or situations. I can't shake the suspicion that someone i know could have raped me and due to my minds inability to handle more emotional stress, i could be none the wiser about it and keep on interacting with that person as though nothing had gone wrong. Assuming i already had serious PTSD and was raped today, how fast would my mind suppress the memory of it to the point where i couldn't remember it at all? And is it possible my mind could cover it up with false memories even just moments after?