Basically, I'm out to everyone in my life except my family. I've told all my lecturers at uni, all my friends, I recently got into a relationship with a straight girl who knew I'm trans before we got together, and I'm currently going through all the bureaucracy and tests on the NHS to hopefully start T before the end of the year. I bind and present as male full time, everyone has switched name and pronouns - I'm pretty much well on the way with my social transition.
Except I haven't told my mother a thing. I'm 21 and moved out for uni three years ago, and since then we've only seen each other a handful of times. The last time I saw all my family was when she and my stepdad got married last year. We're not very close, but it's not because we don't like each other or anything, that's just how it is.
So I don't know why the thought of telling her makes me so anxious. I get the feeling she'd be fine with it (she's very 'live and let live'), and even if she wasn't, it's not like we ever talk anyway, and I've been financially independent for a long time. I've toyed with the idea of sending an email, but I don't think she'd fully understand it. I have no idea what the hell I'd say on the phone.
I feel stupid for getting so worried because I suspect she already knows. We're friends on Facebook, where I have my new name, and for my birthday recently everyone except her and my brother wrote my new name in their birthday wishes (my brother went for my old name, my mum called my 'Hunny'

). My friends use male pronouns for me on there. The few times we've seen each other I've been binding and I know she noticed but didn't say anything. My new girlfriend even met her recently (they were in my city), and called me "he" to her

So, yeah. I guess I just don't know how to word it? I just feel uncomfortable sharing something so personal with her? She'll have to find out eventually, especially when I start hormones, but I feel like it's unfair to have everyone in my life know about me, and for her not to. I am her kid, after all.
How did other people come out to their parents? I just... uh, I dunno why it's so hard. Sorry for rambling.