Maddie:
There are two basic parts to transitioning. One is inward facing and the other is outward facing.
Outward facing transition is really the most difficult in terms of effort. Integrating yourself into society as a woman takes a lot of effort. Clothing, makeup, name change, government and financial documents and friends/family/general society acceptance. Accomplishing that step is nothing to be ashamed of, it is quite a feat.
Inward transition concerns those physiological changes that we go through either as a result of HRT or surgery. Much of this provides us with our inner peace and calm. But little of the inner changes are visible to society. No one knows, unless you tell them, if you are wearing breast forms or are tucking.
And in most polite conversation it really doesn't come up. And shouldn't. Is it polite to ask a man if he has a penis? Or a woman who may have had breast cancer if she has had radical mastectomy and now wears breast forms? Short answer is no.
Likewise in your day to day interactions with society as a woman, the guy serving you french fries or the girl at the makeup counter, doesn't need to know, or wants to know where you might be in your inward transition. If they interact with you as you present yourself, that is all that is necessary.
If within a social setting among friends the question comes up, allows you to respond with a statement that discussions about ones intimate bits is out of order. As it would be were a similar question be posed to a non-trans person.
It really is none of their business. None, zip, nada!
I recognize your internal feelings of wanting to be truthful, especially after a lifetime of lying, but there are limits to what is discussed in polite company.
And I really commend you for wanting to live your life openly. I made a commitment to do to that as well. And it is, to my mind, a wonderful way to live. But it also says that if they don't ask, you don't tell. You don't have to wear a sign around your neck that says TRANSSEXUAL!!! Also, I've found it to be very difficult to just drop that little fact into a conversation.
Now if you are talking about something more than simple interactions and you are bordering on a relationship that might become intimate, you have hit one of the conundrums that bedevils many of us trans people today. Tell/don't tell... what to do, what to do...
That one, I'm afraid has no cut and dried answer and you have to feel your way through that particular minefield without tapdancing too much.
-Sandy