Dear Axa:
What you are feeling is part of the process. The N-individual makes a considerable impact on our lives, and not for the best. It takes a long, long time to get over the experience. I can only tell you that it took me the best part of four years! Yes. At times it was like being "haunted", I swear. The presence was quite overwhelming. It seems this is part of the PTSD we experience.
Let us imagine you were poisoned, but your life was saved. It would take a very long time for the poison to be de-toxed from your system, and there would be times when the after-effects would appear, even fleetingly.
The good news is that one day these episodes are few and far between.
All the best
Hermes