Well... I'm 69.

I began actively rattling around the mental health system where I live when I was around age 50. (Prior to that I had managed to keep the cork in the bottle, so to speak. It wasn't pretty. But I did it.)
My experience has been that, at least by the time one reaches the age of 50 (possibly sooner I have no way of knowing), one is simply excess baggage on the mental health railroad, so to speak.

I have a pdoc. But after 19 years I still don't have a diagnosis.

(I've given up caring at this point.) My pdoc (whom I actually like by the way) will give me pretty-much any psych med I want. If I wanted to I could be on a whole laundry list of 'em. I choose not to go that route. I've also seen a number of therapists for brief periods. They ranged from mediocre to dreadful!

(Of course they were all glad to take my money.)
I also have many questions with regard to what happened with me.

Somehow... I went off the rails, so to speak, very early in life. And in the process I did more damage to more innocent lives than I care to reflect on.

But how or why I know I'll never know.

It makes me sad. In fact it has made me suicidal.

But that's just the way it is for me. I feel your pain...