Difference

So, I'm coming to the conclusion that I'm different.

Not just slightly different, but fundamentally different.

And I don't mean this in a "look at me, I'm a special, unique flower" way, I mean in a "damn, I suck, I make no sense, my behavior does not fit in to anyone's models of human behavior" way.

The more I read about human sexuality, for example, the more I realize that I'm not even in the same state as "normal human sexual response".

The more I read about human interactions, the more I realize that my own interactions are so very different.

And the more I compare my actual behavior to the model in my head of the person I want to be, the more I realize that I am not that person, and therein stems some of the roots of my depression.

I wish I knew why I was so different from everyone else.  I feel like an autistic person, but without a recognized syndrome to explain my differences away.  If I could just find a name for what I am, and a peer group that exhibits the same behaviors, so that I could say "No, I'm not wrong or broken or completely different, I just have Blah-de-blah's Syndrome, and I'm one of .75% of the population that has this, and there are other people like me!"

As it is, even when I run into someone whose brain appears to work the way mine does, such as one of my former girlfriends, I still find that those similarities end up seeming superficial, and she's still orders of magnitude closer to normal human behavior than I am.

And here's the key, it's not merely that I'm not the same, I literally do not understand some "normal" human behavior.  Intellectually I do, I can read the words I can understand the theories for why people behave the way they do, but if I were to act in that fashion, it would be theater, it would be a constant put on act and a conscious decision, and exceedingly tiring to try to do all the time (I spend enough energy trying to behave not-depressed on the days when I am).

So what is it?  Why am I so different?  And why does it make me feel so broken and just wrong?