Hello Doll: Honestly... I would not know what to suggest to you here.

You received a very nice reply from "seeker".

I do think psychiatrists sometimes have a tendency to latch onto the first obvious thing that happens to come up... even if it's not actually correct. (That's just my personal opinion.)

So, at least from my perspective, I wouldn't put too much stock in the psychiatrist telling you your PTSD is related to watching your grandpa die. It could be. But, since you wrote you've long gotten over it, it seems questionable to me.

Spending some time working through all of this with a skilled mental health therapist may help to clarify, in your own mind, what's going on here. Hopefully you're already seeing someone.
There is such a thing as a "highly sensitive person". It's possible the symptoms you experience aren't directly related to any particular incident. They're simply the way you react to things... the way you're "wired" so to speak. (I think this is the case with me.) Here are links to 3 articles from PsychCentral's archives on the subject of highly sensitive persons for your consideration:
https://psychcentral.com/blog/archiv...sitive-person/
https://blogs.psychcentral.com/imper...sitive-person/
https://psychcentral.com/blog/archiv...ing-overwhelm/
My best wishes to you...