Hi everyone,
Sorry, essay coming, with some background about me and some questioning at the end.

Cheers if you make it through all this.
This might seem like a strange thing to ask but, what do you do when you realise you're trans?
I'm in my late 30s, and in the last few weeks I've realised and acknowledged to myself that I'm a trans man. The clues have been there all my life, but I haven't had the knowledge or language to name this strange feeling inside me. It was such a relief doing research online and going to the library to see that there's lots of resources out there these days, but growing up when I did and where I did, transgender folks were not around me and no one was talking about them. As a teen, I had a couple of friends who were LGBTQ, but well closeted, because it wasn't a time or place around here where that would be accepted in my rough inner city school. Both of them came out in university. I'm so happy for teens now that there's more awareness about trans issues, and gender spectrum.
As for me, how can I describe myself? I was/am a tomboy, ever since the beginning. As a little kid, I loved bugs and animals and adventure. I hated dolls, hated dresses, hated being feminine. Until age 5, my hair was close cropped as a boy's. My mom was happy to let me be, my Dad wanted me to be a doll. There was even an incident when I was age four when my dad found me yelling obscenities as I bludgeoned the doll against the side of the house. I came from a very polite family, so don't ask me where I learned the swearing or got all that anger from. About the same age, I went for surgery, and as they put me under, I remember the doc asking me, did I want the pretty dolly or the red balloon. I wanted to tell him dollies were stupid but I think I passed out about then.

And no offense to anyone who likes dolls, they just weren't my thing. As a kid and teen, most of my friends where boys. We could relate.
Teen years were kind of a disaster for various reasons, but luckily it was the grunge era and my friends and I, mostly guys, and generally nonconforming females, bought all our stuff at thrift shops--usually men's clothes. I definitely didn't go for anything feminine in my teen years, make up, etc.
Eventually, I went to uni and became an archaeologist, and I've worked as one for many years, despite being told 'I'm too feminine' for that by father. It's a very traditional profession, especially where I work in my corner of the world. Even though there were quite a few of us, and statistically speaking somebody's gotta be LGBTQ, only one person came out as a lesbian that I knew, out of hundreds of archaeologists, and she wasn't in a mainstream field role either.
In my twenties, I lived in a very conservative place and had a very conservative (homophobic!!) partner. After several years in this uncomfortable relationship, things ended, and I came more into myself in my 30s. I've had some health problems though in these years, especially this last year, that are bringing me to leave the profession, or at least go about working in a different way.
One thing I've done all my life is write fiction. And nearly all my main characters are male and queer. Only in the last while have I asked why, and I've realised it's because I identify with them. And I've realised that I'm still primarily attracted to men, but I want to be seen as male by others, as well as myself.
So that's a scary realisation. I reached out to a local charity and learned they offered gender therapy, so I'm on a waitlist, but it's going to be months before I talk to someone. I did tell my psychiatrist, who is supportive. But I've been freaking out privately while coming to terms with all this -- what it means for me professionally, finally an understanding of why I'm so uncomfortable in my body, etc. And freaked out again when the charity asked me what I'd liked to be called and my pronouns. Made things very real. And it feels like you should have this stuff sorted when you come forward.
So what did you do when you when you realised you were trans? What are the first steps?
I don't even know what clothes to wear any more (I tend to be more fashionable, though lately it's hoodies and jeans). My hair is still long. I'm trying to lose weight, and have lost 10lbs in 6 months, which I'm happy about. Trying to eat well, practice self care.
But I'm pretty sure I'm a trans man but I have no idea where to even start, you know? Names, legal names, pronouns, T, etc... I'm overwhelmed. I did tell a couple people close to me who are supportive, but they don't know what to help either, since it's out of their frame of reference too.
Cheers!