To be insanely self-aware to the point of not experiencing anything?

This might be quite incoherent, as I don't really know how to describe this.

I've somehow developed this way of thinking where I'm extremely aware of the thoughts and emotions behind everything I do. Part of me constantly analyses how I feel, and it kills whatever mood and having and makes me extremely detached from life. Say, if it's a nice day or there's a beautiful view, when looking at it there's initially - and I mean very briefly, like half a second or so - a moment of happiness or awe, then my mind becomes aware of the fact that I'm looking at something I find pleasing and that doing so is initiating positive emotions, and that completely kills the mood, and I just become detached and trapped in my own head again. It started about two years ago, at first just affecting a few activities, but now its spread to infect almost every aspect of my life. Nothing feels real or meaningful anymore, as there's this constant detachment no matter what's happening. I find it very difficult to lose myself in something as I've basically forgotten how that happens: when I try reading, for example, I can't help wondering how this is meant to work, and how just looking at words is meant to give me pleasure, and how anyone could enjoy this - and reading is usually one of my favourite activities. I dread any important event in my life now because of this: say, if I got A*s in all exams or got a dream job, I wouldn't be able to experience it 'properly' and would just be left feeling confused and disappointed. It's not just enjoyment that is affected by this, anger or sadness are extremely difficult to provoke now. For some reason it's worse when it involves a work of fiction, say, if I'm watching a TV show and there's a moment I feel I'd normally be excited or made sad by, then I think, 'this is a part where I'm supposed to feel sad' and that completely breaks my immersion. The only thing I can do to enjoy myself is to do something I enjoy for a really long, uninterrupted period, so I eventually lose awareness of myself and the fact that I'm trying to enjoy myself, then I can truly escape into it for a brief period.

The obvious suggestion here would be that I have depression. I have in fact had issues with mild depression recently but it seems a separate issue from this. The depression means I have difficulty feeling emotions or enjoyment, while before the depression I would feel emotions and enjoyment but in a way that was very detached from what I was doing or my circumstances, and depended mostly on what I happened to be thinking at the time. I could still enjoy things, but whether or how much I'd enjoy them would vary completely from day to day - the activity itself had no intrinsic worth anymore. I can never look forward to anything because of how subjective I know it will be.

I really don't understand why this has happened. I was a fairly optimistic, generally healthy person with clearly defined hobbies and interests, and a good idea of what I'd want to do with my life. I've never taken drugs or anything like that (the only thing similar to this I was able to find online happened to someone who'd taken too much cannabis). Now things I usually enjoy are a source of anxiety to me as I never know how I'm going to react. Even if I somehow resolve this, I'm worried that having experienced this will irrevocably change my worldview. I used to have a passion for life and see the intrinsic wonder in most things, but now life essentially seems reduced to trying to keep up a series of positive sensations by maintaining the right attitude, with actual events seeming only incidental. What terrifies me is that I haven't been able to find any examples of this online or in psychiatric terminology. I feel uniquely broken as if I've broken some kind of taboo that can't be fixed, and now I'm just trapped like this.

Sorry for the extremely long and ranty post (I'd include a TL;DR but I guess the title suffices as that). I've asked my therapists about this (though I didn't tell them the full details so they might have gotten the wrong impression) and they said they've seen it before and it can be dealt with, but I can't get over the thought that they might just be lying to reassure me. So has anyone else experienced this, or known someone who has? Is this a condition, and is there a name for it? I'm not that interested in whether it can be resolved, I just want the relief of knowing that someone else has gone through this too.