I completely relate to this. I wasn't diagnosed until I was in my late 30s, after being told it was anxiety and depression all my life (I do have those things also). The "what could have been" hit me like a truck. It triggered my anxiety which looped into depression and put me in a hole for a long time. My advice to you is to try to find some way to let it go. Your feelings are absolutely valid and it's understandable to be frustrated and angry, but don't let it consume your focus. It's a trap that will needlessly consume a huge portion of your life. The fact of the matter is that it's impossible to know the answer and ruminating on it can only do you more harm.
"Project 2025? Never read it."