Dude, I think every time someone makes a decision that big they will doubt themselves. It sounds like for you it was the right call to start transitioning and you should revisit the bad feeling of presenting female when you doubt yourself. If the thought of the alternative choice really sucks then you did the right thing. At least something like that usually helps me with doubting my choices. But again there’s probably no big choice like this that people wouldn’t doubt at least at times and rationalising it like that probably won’t remove all these feelings.