So there's still some uncertainty?
How did you come to terms with the fact that you'll be chemically sterlizing yourself as you transition and will require significant medical attention awterwards for the rest of your life?
Complicated answer, so bear with me.
On a philosophical level, certainty is an odd thing. I know this: cogito, ergo sum. Beyond that, I would argue that one cannot be certain of anything else. Am I making the right choice? I think so, but the only way actually I'll discover if it's the right choice is if my belief is falsified. Basically, the only way to truly answer that uncertainty is to come to the conclusion I've made a mistake. It's like climbing a mountain that has never been climbed before. There's no established route, and I might find myself in a position where I can't continue and I can't go back. That's scary, yes. Before I started anything medical, I spent a year testing different approaches with a therapist, talking to other transfolk, learning as much as I could.
It's not as if when starting hormone treatment, you sign a contract stipulating you can't stop treatment if you decide you don't want to. You can turn back. Yes, if you turn back, you might not get back to the same exact place you started. Yes, I sterilized myself and beforehand knew that I could regret it -- and actually, I regret not sperm banking. How did I come to terms with that? By educating myself as much as I could to make an informed choice. At my core, I am a scientist: I had a hypothesis, I did my research, and so I tested my hypothesis in the safest way I could.
It's been 4 years, I haven't falsified my theory yet, and I really doubt I ever will. It sucks that I'll be dealing with this for the rest of my life. If I had type I diabetes, I would have to deal with it for the rest of my life too. I think of it like that. I did not choose this. I chose to treat this the best way we currently know how.