You are right that no one can feel what you are feeling exactly the same, and it's hard to get inside someone's head to know what other people are feeling. I am curious when you say you feel like a zombie every day, besides depression, do you know of any medical causes, like medications, hormone levels, etc, for feeling that way?
Having said that about not being able to know exactly how you feel, I can relate to your feelings and have dissociation, anxiety, and depression. I am a similar age to you and have similar experiences, and I think for me the two issues i contend with are 1) a fear of change and 2) a feeling that I have lost the years of my life that were supposed to be lived in youth and that pain of the irreversibility of not being able to get that back.
But then again, I've always felt that way at every age to some extent. I've always had a fear of failing, and then I kind of really did fail in a big way in life when I dropped out of college for medical reasons.
I think you and I are similar in that at least for me the courage to find a new way of living is very hard to summon. Because it won't be like the fantasies of what my perfect life should be like.
I talked to my dad today about this very thing--comparing myself to friends who are lawyers and have PhDs. He told me something helpful, which is that you can measure your success by the things I look at, or you can at any moment measure by whether you are adding to life and changing, and counting that as success.
And there is some truth in that because I can remember times where successes that I now feel would be too small to count for anything actually did *feel good in the moment*. So in the viewpoint my dad was talking about, I took it to mean, or expanded on it by thinking, we really are all equal. The idea that my friend with a PhD is better than me is sort of an illusion. Because either of us could be happy in the moment and feeling successful or not (and there are people with advanced degrees, famous actors, etc. who feel not good enough).
It's important to remember that what you want is a feeling, what you feel like you are missing right now is a good feeling, and in my experience, that good feeling, even if it takes months, comes back, even if only fleetingly, and it's worth living for.
Hang around just to observe life if nothing else. We are all made of the Universe, and as far as we know as humans, we are the only creatures in the Universe that get to see it, and think about it, and explore it. Your life would be worth living in my opinion if all you did was sit in a forest staring at trees. Or just staring at your ceiling. It really is something in itself just to see it. And to be honest, that doesn't sound like something that would make me happy at the moment. I'm a bit depressed myself. But we don't have to be happy. Thinking we have to be happy is a source of unhappiness itself.
The bottom line is that the reason to live is that you don't know what will happen in life. You don't know how you will feel. I know it's hard when you feel the anxiety that depression causes in the mean time. For me it is an anxiety--a very urgent driving need to find meaning. And it can make you feel as if you can't find it right now you have to cut your losses. I know the feeling. I think anxiety/depression is a good term for it, even though it might not seem like anxiety.
Since you are in the more active stages of thinking about suicide, it might be time to call an on-call doctor or go to a hospital if actually start to act on these thoughts. It doesn't mean you're crazy, it doesn't mean anything bad about you. It's a part of life that some of us go through, and calling a doctor or going to a hospital is just a way of making sure you eliminate any risks of not surviving this period.
I don't think there is such a thing as a non-botched, painless suicide. You are already living with the feeling of being a botched person in pain. It is terrifying to address feeling like an incomplete, not good enough person. But that is where the courage to be comes in. Do it at your own pace, and look for the help to be able to relax these thoughts as you are able to do that. Maybe you need some medication to help you through this period so you can deal with the feelings of inadequacy in a less urgent, more distant, less scary feeling way. There are quite a few coping mechanisms. Your video game is a great way to dissociate. I have had anxiety, OCD, and medications all as ways to dissociate from the things in my life that scare me, and they all have been necessary to some extent. We can't feel everything at once, and when it becomes too much to feel it, you deserve a way to not feel all that pain at once--and there always are ways to lessen that pain that don't include suicide.
In my opinion, of you, and of all human beings, there is nothing you could do to fail in my eyes. And I believe all human beings are inherently good. Keep up posted.