Or rather, when people ask me about my life in general. The absolute worst is when I'm doing something on my PC next to someone and they look at my monitor and start talking to me. I just can't do it...I completely lock up, freeze and try to breathe. I don't know what's worse, the gnawing feeling of someone's eyes on my monitor, which to me feels like a massive invasion of privacy for some reason, or the fact that I'm being disturbed, forcefully having my attention directed away from what I'm doing. It's why I strongly prefer to sit in a place where nobody can see my monitor, not even from a reflection. I'm not even doing anything I should be ashamed of, I just fucking hate the feeling, honestly.

This isn't new. Even at 10-11, when me and my mother were walking, she used to ask me about the book I was reading. And I just...froze completely. I felt like I was being interrogated for no reason at all. So I stopped talking. She got upset, ofc and I got upset too. And...that wasn't the only time this happened. Every time someone asks me about what I'm doing, I know they're gonna be upset, I know exactly what's going to happen...but it's always the same anyway. I just can't...talk. I don't want to. Why won't they just leave me alone? I hate it...

My current bf. I've told him multiple times to not ask me what I'm doing. I said that if I felt comfortable, I would tell him myself. Well...of course he doesn't respect that. Just like many other things I ask him to respect...
And every single time it's the same. He asks, I shut up completely cause I feel I can't tell him, he gets upset, I get upset and start crying and then we're just both pissed at each other...all because of me.
The monitor thing is even worse tho. I hate it with a fucking passion. Our PCs are next to each other (I have a laptop), but I do my best to always move to a place where he can't see my screen when he's sitting next to me. Because he always does...no matter how many times I ask him, no matter how hard I try to explain how fucking awful it makes me feel...nothing. So I sit away from him every time.

I don't know what's wrong with me. I don't know why I'm like this. I just wish people would let me work and rot at my computer in peace. It's not like them asking will make things any better. With me specifically, things get much worse. And...I'm starting to kind of blame myself. This is definitely a me problem...

Usually when people ask that it is an open invitation to spend time with and talk to eachother. It is entirely okay for you to deflect the question but still accept that invitiation.
"What are you up to?"
"Nothing much. How about you?"

That persons goal probably isn't to snoop into what youre doing, but to check up on you or have a casual chat. Punishing that good will is not good, but so is them not respecting your boundaries.

Keep in mind it is also entirely okay to tell them you're busy and to leave you be.

I 100% agree with it feeling invasive when people look at my screen, even if I never have anything to hide!

I know it's sort of irrational so I try to ignore it, or if it gets to bothersome I do something small to reclaim a sense of control: like turning one selected screen towards them when showing what I'm working on to guide where they look instead of staring at my whole setup, or getting real quick with the alt+tab to go to whatever open program I decide it's OK for them to look at while we talk.

I said that if I felt comfortable, I would tell him myself.

How often do you tell him that stuff without being asked? If you shared more frequently perhaps people would ask less?

This isn't entirely your situation, but I'll share nonetheless, because I want you to feel less irrational.

Like in many other cultures, probably, people here ask "what's up?", which can be answered in a multitude of ways: what I doing, how I am doing, what is my physical and/or mental condition or - which is most frequently the case - "good", which means nothing. It's a replacement of "hi/hello".

Regardless, my brain doesn't work that way. A "what's up?" is a "how are you doing?" PERIOD. And since at least three years now - I guess that's when the depression set in or whatever - I freeze every single time upon hearing "what's up?" I lose the ability to speak, my brain overheats and I panic: what the fuck am I supposed to do here, knowing that they intended to say "hi" but I can't or won't interpret their "what's up" as such. I have been trying to CBT myself lately, literally practicing in front of the mirror saying "pass", "not right now", "it's bad" or altogether disregarding their "question" countering with a "what's up" right away instead. All the former variations are often followed by a "what's up" from my side to be nice.

While inside I feel "leave me the fuck alone, what do you expect me to say, of course things are bad, what a stupid question, asshole" I never project this onto them, since they are 99% of the time just behaving "normally", according to society's rules. I often force a smile when saying any of the above and then bounce ASAP.