Here's the letter! (Spoilered.) Fingers crossed...

Hi Dad, I have to tell you something that's really important and life-changing, and that's been building up inside of me for years and years, ever since middle school or even really before that, subconsciously and then getting worse and worse, more and more obvious, until I just couldn't take it anymore. I need to tell you this, and do something about it, in order to live the rest of my life at all, let alone a happy and successful one.
Remember how I mentioned that I was really depressed starting the last couple of months? What I'm going to tell you is the reason for that, but I want to go back to my middle school times first.
Back then, I remember having some thoughts that I was just...different from everyone else. I didn't know why or how, but it was already starting to get to me. Like I didn't belong, like I was being excluded, like no one ever noticed me or cared about me or even knew I was there. Do you remember that winter math camp in Las Vegas we went to that one time? When there were a bunch of kids there doing some physics activity, I went into the corner and cried. Not just because I didn't understand any physics like they did, but really because I felt alone, like I was almost some alien or someone who didn't "deserve" to be there because I was stupid or not worthy.
This included thinking about the world differently from how boys or guys seemed to think of it, and how they seemed to talk and behave, and the interests they seemed to share. I just...didn't feel like I fit in with them, or that I was one of them.
I just thought I was an introvert, like an extreme introvert, a hermit, and I thought nothing of it. I always just told myself that was who I was, that was my personality type, and I was maybe socially awkward, but I could work on it later and at least get better at dealing with my surroundings. I got better in later high school, and college, to where I could at least interact with people and make friends and deal with social situations. But I'll get back to this.
Around puberty, around when I started high school, I started getting a bit of a better idea of what this was, but of course I still didn't REALLY know the truth. I started getting more and more attracted to girls, and of course, we all just thought that was me becoming a teenager and falling in love with them, and having crushes that everyone has at that age. I never thought to put the two together, or that anything was even really wrong. And then when I looked at myself in the mirror, it started feeling less and less...right. Less like me. More like some stranger in the mirror, and I didn't want to believe it was me or my body. I felt like, and I still feel like, even more, that I'm ugly and "how can anyone even stand to LOOK at me or LISTEN to the sound of my voice? How can my parents even call me CUTE with a straight face?! That's so obviously not true!" That's the reason I hated being in any pictures, and I DEFINITELY didn't take any selfies of myself whatsoever. Now, again, I'm getting back to this later.
When I started at Berkeley, SOMETHING still didn't feel right. I thought graduating high school and finally starting to see myself grow up was going to end my confusion. I thought maybe I just looked like an awkward teenager and that I'd grow out of it. Well, I was wrong. If anything, I didn't seem to change physically AT ALL after around 14 or 15. Even now, I still look 14 or 15, and no one around me really disagrees with me. But at my orientation, I gave up on it after the first day (out of four) because I couldn't stand the exclusion and not fitting in with anybody, and I almost cried while tossing my milk cup in the trash. It was getting too much for me, but I didn't know what it was, even at 18, and I thought I just had to deal with it by escaping through my studies.
Well, escape I tried to do, at least until COVID hit. And then I was stuck with myself, nowhere to go and not even being able to enjoy a trip or a vacation or relax. The schoolwork was getting harder, and research was the toughest school-related thing I've ever had to do. Nothing I did ever felt like it was enough and I felt like I was trying to do the impossible. Every little thing would get nitpicked and I felt like there was no hope for me.
SOMETHING was making all of this much, much, much harder than it ever needed to be. But I was still in the dark. Totally clueless. WHAT was this thing that was killing me inside so much?? All I knew was, it was getting worse and worse and my classes were magically getting harder and harder, until the last semester when, that, whatever it is, plus grad apps, were just making it so hard to get through that I literally had to count down the days until the semester was over and I could graduate.
But FINALLY, all the worst was over. I graduated from one of the top schools in the world, and finally it was just time to sit back and relax...right?
Wrong. The thing, whatever it was, hadn't even started with me.
This year, the feelings kept building up, more and more and more, until they just...burst. And then I told my mom, and we've been trying to work on it, together, for the past six months.
Everything from the past suddenly made so much more sense, when I looked at it this way. My feelings about feeling and thinking and seeing the world "differently" from everyone else, especially boys or guys, my feelings toward girls, which were closer to envying them and wanting to BE them, than just a simple romantic attraction...
It all makes sense now. It turns out that I'm actually transgender.
What that means is, even though I was born as a boy, my brain has the uncontrollable urge to be and live as a woman, and not being able to present as one is giving me a life-threatening medical condition known as gender dysphoria.
I mentioned I was seeing a therapist for my depression (since March). I just got an official diagnosis from her for gender dysphoria a few days ago, and I put the letter here for you to read.
Basically, it's a neurochemical mismatch between what my brain expects (maybe caused by hormone levels and certain types of hormones flowing into the brain during pregnancy, but no one really knows for sure), what it's wired to expect, and how I actually look. This means that being trans wasn't a choice. It just happened, and it's who I was born as beyond my control.
It means that the way society treats me, from seeing me as a man, is entirely wrong to me, and trying to live with it has caused me so much accumulated stress and trauma and even mental instability that it's starting to ruin my life.
But when I even do something as simple as apply some makeup, or change my clothing to women's clothing, or imagine being called "she" instead of "he," suddenly some of the dark clouds are lifted. Not all, but some, enough to temporarily escape into a heavenly world. In those few moments, I never want to go back, and I feel (halfway) like the person I've always been on the inside. It feels right, it feels true and authentic to who I am and have always been, and I'm 100% sure that it's something that would be right for me.
Here's a link that helps a lot of people understand what gender dysphoria is and why it's such a big deal. [link to the GD Bible]
Part 2:
I know this is...such a big thing that's going to change my life forever. But the truth is, despite all the risks and challenges, it's either this, or...nothing. Either I do my best to transition according to the medical need of my brain wired that way from birth, or...it's possible I might literally be dead by suicide in two or three years, or even one year.
Without transitioning, I literally can't function. What dysphoria's doing to me now was unthinkable even a few months ago. My emotions (especially positive ones) are almost non-existent, since they're either just a blinding rage or complete numbness, I can barely get up to do things, I can't get any serious work done, my levels of self-hatred are at an all-time high and my self-esteem at an all-time low, I have panic attacks and full-blown mental breakdowns every 4-5 days, I can't even accidentally glimpse at any women in public without going through intense gender envy and feelings of hopelessness, coping techniques are getting harder and harder (even exercise, which used to work okay as a distraction, is starting to get less and less effective, and same with listening to music I used to love but now feel nothing when listening to), and my relationship with Mom is very, very complicated, because I've gotten in such a low and nasty mood that it's souring things between us. If it keeps up this way, there's a very high chance I would flunk out of grad school, because I can't focus or study or do anything, and ruin my entire future anyway, and that would only push me onto the edge of considering self-harm or suicide.
I know I need to avoid this, so transitioning is really my only option. I'm still taking time to adjust, myself.
I'm still attracted only to women, and not men at all, which is another thing that could put obstacles in my way, but again, to me, it's either this, or no future at all, and in the worst-case scenario, death.
I hope you can understand, and I would really love to have your love and support, like you've always given me, even if it does take a long time. Please feel free to let [relatives] know too.
I understand, and I get it. It can't be an easy thing to swallow. I'll give you all the time and space you need to think about and process all of this.
But you're my Dad, and I love you.