One of the most difficult things for trans-women to "get," imo, is exactly what tekla said: the ambience of conversation. Not all women talk about child-birth, nor do they talk always about periods or other aspects that will make you "different."
Many of them, more than most trans-women are aware of, haven't periods or have very irregular periods and/or are unable to conceive children as well.
But the tenor of the conversation, the ease that things move through many more levels and categories, sometimes simultaneously seem to place trans-women who often have had either very little interaction with other women or have had typical male interactions with other women at not simply a disadvantage but at a loss of how to move through those conversations.
Suddenly there is, as Kat said, no expert opinion, no rote or accepted way of doing things that is available to her, or to them. And yes, at that point one may well focus more on her sense of "how do I go about this" or "are they gonna know" and lose whatever confidence she has built into herself for conversation.
In other words, her conversation, her internal conversation, reverts back to "what will I say" and makes the center of her internal conversation "me." That can happen as well with non-trans-women in some instances: where the topic will become, quite naturally and unforeseen, about something that she has a personal, a very personal, stake in and that she doesn't share with those others.
The major difference I have found is that the trans-woman will often show her alienation from the conversation, become more withdrawn, less confident. The non-trans-woman will often begin to talk about how she doesn't fit in with the others and in doing so will be able to allow the others to include her experience and/or sorrow into the conversation.
But, the "center" will quickly become normalized back to the group as others will begin to normalize the experience of the "outsider." Trans-women generally have no experience of that in their conversational backgrounds and will, possibly, believe that they must recount their experience or make-up one. When short and shallow remarks are probably more indicated by the context.
The trans-woman will often guide the conversation to an area where she is comfortable.
That is the infamous "taking up space" that many of us have read or experienced with men.
One of the reasons I would almost always suggest that trans-women find and become a part of the company of other women rather than the company of other trans-women while transitioning. To learn, we need teachers, not those who imagine we know what we do not, but those who do know.
Listening and hearing become very important prior to and during transition. And that is generally a position most male-raised people do not grok very well: for the priority in male conversation is very often a matter of "establishing authority" (not control
per se, but the establishment of a kind of credential for making one's point, an expertise.)
I find that usually many degrees down the conversational importance scale in conversations among women.
Cultural & social? Prolly so. But still, even for that, quite important to discover and incorporate.
Now, the one thing we are leaving out here, Dora, is why do
you think you become less comfortable? Is it what we have said or is it that you find yourself "passing" and feeling more uncomfortable with that aspect of your life than you might have imagined you would? I'm thinking it's time to normalize the conversation and get you included rather than get you "taught."

Nichole