I can surely relate. I had all sorts of mental and physical symptoms (and still do, sometimes). Palpitations, brain fog -- and like you said, the feeling of losing my mind. I've gotten medical clearance (from my internist and a specialist), so I'm with you there: at least I know that it's a psychiatric issue.
I still need to find a trauma therapist, but at this point, I'll settle for a therapist/psychologist who has some experience with it, even if s/he doesn't specialize. Good move, and it sounds like it is beneficial. Congratulations on taking that step.
With respect to intrusive images, I personally cannot control their frequency or intensity, and they bombard me.
The best I can do is step back from them, and detach my emotional reaction to them. I find this helpful. If I can't control the thoughts, at least I can control my reaction to them. Or at least I can try. It gives me a sense of control in an otherwise panic-provoking situation.