Bottom-line? Yes, people often have doubts, often delay for even years over whether or not to transition.
Truth to tell, from what you've written your doubts appear to have been placed there by shrinks and a prof. Hmmmm. The staid advice is always to "go-slow." In terms of discovering yourself and moving into a different way of presenting yourself to the world, that's prolly pretty fair advice.
But, you've also gotta try to see who's talking to you and why they might be saying what they say. 1) First off the shrinks will be looking toward mental illness. I mean it's fairly natural. Think about it, hammers think everything's a nail often enough. 2) If the shrinks and the prof are male I can also pretty easily imagine there's a component of "self-preservation" at work as well.
Imagine them sitting there, considering from a pov that basically has never had the type issues you have with "identity," contemplating the fileting of their penises and living their lives as females. Sorry, but I know from experience a clinican of any kind is NOT going to be totally able to view these matters without their own ideas and feelings coming into play. The prof maybe moreso than the others. Just a fairly factual explanation.
In fact, at your next sessions you might ask them, you really can ask questions of your own to these folks, how they think they might feel about doing a transition. Try to hold them to the point and not accept deflections (we call that re-direction, as in turning you around.) Then you might get a better idea of where they stand internally.
3) You appear from your post to be pretty firmly decided on a couple of things and one is how you wish to live your life and who you find yourself to be. That's very good. 4) There is no guarantee that as you get older your body won't feminize well. But, you are also pretty right about better results being more available when you're younger.
If the doubts are yours then explore them. Try to discover what the deep-lying thoughts behind that are if you can. If you're simply hesitating due to the "go-slow" advice then look at the "vested-interests" of the people telling you what they've told you.
O, not all female gender-therapists are totally accepting of the validity of "gender-identity" either. They could also have their own set of qualms about your transition.
It simply pays, Chrissi, to know where those doubts you say you have, but don't name, are arising.
All the best. And please do keep us posted.
Nichole