I really don't know where to begin. And, I don't know that there's any "real" advice to be had. Just thought that writing things out might be therapeutic.
So, shorthand - I have always presented as more masculine, but have almost always been read as female. I have simply never like women's clothing, haven't worn make-up, have had short hair for decades, etc. And, as a lesbian, I was pretty much fine with that. I've been familiar with the possibility of transitions, and have known several FTM for a few years now, MTFs for much longer. It's not like I was clueless to those options. But, I never felt compelled to transition. Yet, neither did I conceptualize what I already had, a non-binary identity. Now, realizing that there are options, I feel compelled to 'push' it. I definitely identify as transmasculine non-binary. Yeah, people debate the terms. You get the picture.
I don't really have many changes to make in terms of hair, clothing, etc. At my age (let's jus say I'm closer to retirement than to starting my career!), I don't really care about pronouns or even my name, though I've started using a more gender neutral version. Having worked at the same place for twenty years that would be too big a hurdle. No, what I really care about is more personal. I have, for years, wished my breasts would go away. I've always wanted a more male - or at least androgynous - physique. And, the sexual, well, TMI.

So, I'm really not struggling with what I
want. The question is (drum roll, please) how to address this with my partner of almost twenty years. On the one hand, we've both talked about what a pain in the neck (not literally, I'm not that big) breasts can be. But, she will not want to see mine go away. I am fortunate in that I could schedule surgery and pay for it out of pocket if need be. The only thing holding me back is broaching the conversation with a partner who is fairly conservative, not politically, but socially, for lack of a better word.
I had my first therapy appointment yesterday. He was fine. I told him the above and he seemed most pleased that I am thoroughly content with my identity. It, in and of itself, is not 'an issue.' I talked a lot about relationship and health stuff. And, we scheduled three more appointments. It kind of freaks me out to even write what I've written. I'm pretty sure that she doesn't know this site exists, but if she did stumble upon this post I think I'd have outed myself. And, no, I don't secretly want that to happen, but I finally decided I had to put it out there and see what others might have to offer.
So, I guess the nugget in all of this is - forget parents, who out there has dealt with 'coming out' to a long-term
partner who will likely not want to terminate the relationship at all, but will have some real misgivings about the whole thing?
Thanks for your thoughts. Be well.