First you can phrase things a little bit differently and adjust your narrative a bit so it is true, but leaves out certain details and you can move forward without feeling like you are lying about anything.
The way I handle it is I am not ashamed of my past, and will own it proudly if it comes to light, but I consider it private info that is rarely relevant and don't openly share it with anybody. And yeah my narrative is adjusted, I will never say 'when I was a little boy' mostly because I do not believe I was ever a boy. I did live as one though. Anyway, I usually just say, 'when I was little' or something along those lines. It works.
The term transgender, nope I don't use that. Trans woman, ok, that one is fine I suppose. Adjective noun, like tall woman. It's ok. No transgender, no acronym nobody has heard of, and I avoid transsexual cause I just don't like how it sounds, but meh, I will use that one too in a pinch.