Is there a particular problem you have with medication? I know it takes a lot of work to get meds that actually work for you and in the meanwhile you're getting side effects with little to no benefit, but getting to the right mix can do a lot.
I really don't know how to help you, and I don't know if I've ever felt what you're feeling. My adventures in depression have never lasted very long. So, what I'm saying might be functionally equivalent to, "Just stop being depressed and you won't be depressed anymore!" I know that it's a shitty feeling to be constantly hearing advice like that. "All you've got to do is quit drowning and you'll be fine! Just swim!" is not exactly good advice on how to survive a shipwreck. The point is, I might completely miss the mark by talking about things that have helped me, because you aren't me. If my words are unhelpful, it's not because I think your problems can be easily solved by the advice of Internet Guy #4241133, but because the insights that helped me aren't meaningful for you, and unfortunately there's nothing else I can offer. Basically, if I'm useless to you, that's my fault, not yours.
All that said, a thing that's helped me when I get locked into feeling like everything is shit forever is to decontextualize things that I think about. Avoiding thinking about what's happening to me or what it means for my life or the world in general. When I start doing that, and I'm stuck in one of those spirals, I can't help but assign negative value to everything, and that only convinces me that continuing to feel like shit is the reasonable thing to do. I didn't have a shitty day - a bunch of shitty things happened, sure, but I don't want to draw conclusions about the entire day. In fact, I don't even want to think of those things as "shitty", just as "things". One of the biggest themes I'm seeing in your posts is that you're devoting way more effort to describing how awful everything is than to describing what everything is. That's not really unreasonable - after all, how you feel is a lot more important than the exact events, when what you feel is a crushing sense of life's worthlessness and the exact events are you had a bowl of cereal*. It just cements that feeling as the "right" way for you to feel, and that's ultimately a big part of the problem. It's not just that you feel like shit, it's that you also feel like you're perpetually surrounded by evidence that shit is how you ought to feel.
If you can find a way to wrench your thoughts away from looking for that evidence, it can be very helpful. Instead of thinking about how your birthday is a hallmark of anything at all, just note that you're going to have to add a 1 to your age on forms you fill out, and move on. It's just a day, like any other, after all. If your mind is going to insist on telling you that nothing matters, try and make your brain accept that nothing matters and stop trying to make you feel like that matters. Once you get there, you can start moving toward defining your own metrics of value and so on or whatever it is that people do to stay sane.
*This is a real thing that's really happened so hopefully I'm not coming across as just being flippant. I mean, I am also being flippant, but the fact is that some days you realize this you've been eating the same breakfast cereal every day for a month and what started as a one-off whim has become just one more pointless ritual that serves no purpose but to carry you on toward the next such ritual and that's how you get from "Whoever decided that chocolate cereal should leave chocolate milk is amazing" to "My life is a complete waste of energy and effort" in less than a minute. I... don't eat cereal much these days.