Now, where should I start?
It looks like I'm a great liar, having managed to keep a rather fundamental truth from myself for the most of my forty-odd years. As to what that truth is, I'll give you one guess.

I live in Northern Europe somewhere between Scotland and Russia, with a wife and one child. I work in an academic environment, and during my career I've been trying to decide between two rather different fields (see a pattern here?). In that context, of course, it's called being interdisciplinary instead of having an identity disorder. Still, one reason why it took me so long to figure out what was going on was that I have a couple of other aspects of my life where I'm in some sort of an in-between position -- gender was just another one. In a sense it's been a relief to realise the truth.
I still don't know what I'm going to do. In hindsight it's pretty clear that my identity is female. It's less clear, however, just what that means with regard to my physical and social gender. Socially, I've never been very masculine (although I have tried every once in a while), so I'm not sure I have a pressing need for a major change. Physically, I'm not sure going on like this is too much different from coping with any other serious disability like, say, losing a hand in an accident. Anyway, figuring out what's going to happen will take quite a bit of time, so it's likely I'll stick around.
The name, by the by, is modelled after that of the 12th dynasty Egyptian Queen Sebekneferw (meaning roughly the beauty / goodness of the then royal patron god, Sebek); Seshat was the goddess of astronomy, math, writing and assorted related matters. And no, I'm not an egyptologist.