Female here. I picked this username many moons ago and never really did like it. At least people pronounce it right, unlike my real name.
I’m a guy.
I have female plumbing, but never really felt like I was doing a very good job at being female. Most of the time I’m androgynous, in the sense that I don’t really feel like a girl or a guy. I’m just me, and of the opinion that unless it’s somehow related to sexytimes (and since I’ve been happily married for almost thirty years that’s unlikely) it shouldn’t really matter what gender I am.
In spite of the “a” at the end of my name, I’m a boy.
You are way over thinking this.
Anyway, I’m a man, man, just like my handle implies.
Male to date.
So, named after the last tube you used?
“My name? H.
Preparation H.”
Woman, no question about it.
beep i leave that for my minions beep
Over here they’re spelt “huevos.” 
A lot of people are. I didn’t expect this to descend into mass self-reflection and debate, but how long have I hung out here? I shoulda knowed better. :o
I am reminded of the classic New Yorker cartoon with the caption: **On the Internet, nobody knows you’re a dog. **
Woof!
(I assume my username provides the answer to the OP question)
Boy, with boy parts, identified with masculine pronouns.
Hubba, hubba!
As the name implies. 
You’re a flower? A wonderful variety of rice? 
Female
But that’s not really it, either. To the extent that I call myself male, it’s because I’ve spent most of my life being told that a person with a penis, etc. is male. When I describe myself as a man, it’s because that’s the description people expect for a balding person with a moustache. It has nothing to do with any inherent sense of how I think about myself, and so when someone else who has a penis, and who would grow a moustache if not for regular shaving, and so on, says that she’s “really a woman”, I have no idea what she means by that. I’ll still refer to her as “her”, and so on, if that’s her preference, because that’s only polite, but I don’t understand it.
I am certainly no expert (and maybe this is not the right thread for this discussion), but for some people it has everything to do with an inherent sense of how they think about themselves. Even tho they, like you, have been told all their life that they are a boy, that just feels wrong to them. They know, deep inside somewhere, that they are not a boy. That no matter what their physiology says and no matter what their family and friends say, they are a girl (or vice versa).
Maybe when what youve been told all you life matches up with how you feel about yourself, it’s hard to tell one from the other - they meld into the same thing.
mc
I’m a woman, though I often get mistaken for a man.
I’m a dude.
Tripler
And yes. . . I abide.
But that’s the thing. For me, neither is right. It’s not important enough to me to fuss over it, but there’s definitely a feeling that although ‘girl’ isn’t exactly right, ‘boy’ is just flat wrong. But it truly isn’t that vital or important. So… what’s the point of being all snowflake about it when it doesn’t matter that much?
It’s not like there’s a particular identity that I resonate with to tell people to please call me x. So since there isn’t an option, and since the default social option is somewhat close anyway… eh ok?
But I still feel like it’s not quite right. I guess if this whole pronouns thing gets rolling in general, ‘they’ is a good alternative option (‘it’ feels a little too dehumanizing) but really it’s not like I’m offended or confused or upset at feminine pronouns.
On the flip side I’m also not upset when people online or at work think I’m male (my real life nickname is more commonly a male name: think Mike or Jo), but that’s usually because that means I get treated more respectfully and am less sexualized or infantalised by the people talking to me. It is however sometimes a surprise for me (when meeting in person the first time, or talking on the phone) that the other person DID think I was male - I had just been assuming they were being polite and professional.