Moni,
It's the emotional part that is key to understanding that you are non-binary, you become aware, just as you did about your gender, that yours is solid and dependable, just not the one on the ticket issued by the hospital based on your sex. For us it can be solid and dependable, but in two directions, so for me, there are certain environments that my behaviour is predictably female. However (and this is why I'm NB), there are certain environments where I respond in a way that is atypical for both binary genders. As an example, I can quite literally sit as a translation machine between two married heterosexual partners, and interpret both ways. When that happens it's obvious to me that I fit in neither, because I observe both. That's as confusing as hell, but for some it doesn't happen often. Or for others it's very often, either way, you can be expressing as one gender, and in the main feel ok, but there will be something that is difficult to pin down that interferes with emotionally connecting and being exclusively just one gender. Until of course you hear about NB, the penny then drops, and you realise 'of course I felt off, in these situations I respond, engage or react like z gender' and the puzzle fits together.
For us, it is a puzzle that some work out, and others spend their life trying to work it out.
Does that ramble help.?
Rowan