First, I don't think there's enough in here to warrant the TW flair, but TW for suicide mention, violent thoughts and self harm related themes. 

Second, I know the title is a question but this actually took the form of a vent more than anything hence the flair I did use. 

Anyway, I've known for pretty much my entire life that I view things differently, almost as though I'm not actually living, but rather just observing life through a random sack of flesh. Like, I can become friendly with some people, but I can't feel like I'm friends with them. I would be aware I was getting cold, but incapable of actually feeling it. But simultaneously I would feel constantly on edge. I would see the shadows in my bedroom take the form of people holding weapons and move towards me. My curtains could see me. Computers wanted to kill me. I was convinced that cars would suddenly accelerate and run me over, whether I was crossing the road or on the pavement. Hugs would lead to me being stabbed in the back, literally. Everything was too bright, too loud, too confined, too much. But throughout my younger years, I was as okay with it as I could be. 

But when it first hit me that this experience was "wrong", I came to the conclusion that I was only semi human. I would be incapable of providing or feeling any real sort of care or affection towards another, but I didn't want to be cold. So I went to measures to try to make myself real. Self harm in the "traditional" way as well as indirect ways (my apologies for the dodgy phrasing, I didn't want to accidently break the community rules regarding not depicting SH). That developed to the brink of a suicide attempt.

It didn't work. All it did was make me essentially addicted to pain, in trouble at school, and give me some very vivid thoughts of self harm and suicide almost constantly going through my head, even when I slept. But I didn't seek help, because nothing had ever happened to me to incite this behaviour. Literally nothing. I had a stable family, a few decent friends, lived in a safe neighbourhood, etc. I didn't have anything to get help for. It was just an "emo phase" in my mind. 

It got worse. As well as what I had been experiencing, I now got noise-related violent thoughts. For example, I would hear someone chewing  gum and I would want to cut their tongue off and shove it down their throat. I had come close to trying to kill myself on numerous occasions and had actually tried by this point. Then my neice came into existance. It's so loud and nobody tries to stop it. And it receives so much more love from my parents than I ever got. 

That is the recent development to make me ask if you can get a mental condition  from nothing at all, for now I also get thoughts of smashing its things against the wall so it can learn to be like everyone else. While I don't think of harming it, I am concerned that this could escalate to that kind of situation. I don't want that to happen, but in order to prevent that, I would possibly need some form of support as I have no idea how I'm supposed to be or how I'm supposed to function. But I can only get that if there is a condition there to begin with and I don't know if a condition can be from birth or if something actually needs to happen to a person in order for them to develop one.