Fear of invalidation; please help?

Hello there :smilewave

So I've been questioning my gender for a couple months but never really delved into it until this past week. I've come to the conclusion that I feel genderfluid. I looked back on how I feel and my past experiences and drew my answer from there. I experience minor body disphoria (usually negligible if I'm not a wreck that day, rarely severe) irregularly, sometimes want to have a boy's body, other times I love that I have an hourglass figure. It's quite often that I wish I had a more androgynous or gender neutral body shape so that I can dress according to how I feel that day. But I don't. :bang: I am literally the epitome of a traditional feminine body. Older family members often try to compliment me on being dainty, curvaceous, and definitely not "packing on the pounds", but it often irritates me. Only on the days when I really feel like a girl do I truly accept the compliment.

I have a friend who is trans. He is kind, understanding, and just all around awesome. My problem with coming out to him and my other friend (we make a nice triangle) is that I never really had much knowledge or understanding of gender expression, pronouns, all of that stuff, when I met them. This is almost a year ago. When I began hanging out with them regularly I never had much trouble with the right pronouns. I've only slipped up a couple times because my speech get jumbled when I talk about several people at once. I actually cut ties with a friend over their disrespect for my trans friend when we were still only acquaintances.

I've come out to my other best friend as asexual, as well as a few friends in my art class. But I haven't come out to my trans friend because I hate feeling like I'm just deciding to be a certain way simply because I met someone who doesn't follow the social norm. I've been thinking of ways to come out to him as asexual, and now there is my gender-fluidity.

The main reason I'm having difficulty in coming out to him especially is that I know there are people in the world, even in our school, who declare themselves to be something just for attention. That's my problem. I don't want to be viewed that way, especially if a person pretends to be accepting and welcoming of it but then invalidates me behind my back. I don't think my friends would do that, especially my trans friend, but the fear is there. I don't want him thinking that I just decided to 'become' genderfluid because he is too and what great friends we are, twinsies, blah blah blah. I feel that people who claim themselves to be something for attention invalidate others who are most definitely not doing it for attention. I've experienced invalidation from the former friend I mentioned above and from my mother concerning my depression. I've also had my mother invalidate my reasoning for wanting a breast reduction (macromastia). So yeah, I know how it feels and I never want to feel it again.

TL;DR
My fear is crippling and I don't want to insult my best friend, even though I know I'm not doing so.

Any advice or motivation you could spare? Also, I have no idea how to come out to someone purposefully. When I came out to some of my friends as asexual, it's because we were on the topic of sex and sexual relationships and I was asked for an opinion. Also, I am very emotionally unstable, so I'll probably cry out of anxiety and fear if/when I come out to my best friends.