For myself, I've found something that appears to help when I get into the state where nothing feels meaningful. That is focusing on gratitude. In other words, I spend time looking for things in my life to be thankful about. When I first had the impulse to try that, due to reading an article about it, the result was immediate and for my inner experience, everything seemed to suddenly transform into something radiant. The "nothing feels meaningful" state just vanished entirely in moments. However, the next day I needed to spend half an hour doing that for the same effect.
That was ... maybe a week ago? I haven't needed to actively concentrate on gratitude since, so the effect appears to be reasonably long lived. Still, since it's on my mind now that I'm writing about it, there's a noticeable effect already.
Anyway, I realized that it's been pretty rare for me to actually feel gratitude. I suspect an overload of fear tends to override feelings of gratitude, so it would make sense that I was doing too little of it. It's difficult to feel gratitude when you're feeling (imagined and unconscious) fear of death whenever you actually try to do something. It might be due to having been able to significantly reduce that that I'm now able to consciously activate the feeling of gratitude.
Try to find the source of that self loathing and eliminate it. It should be an unconscious belief of some sort that you really would be better off without. If I had to guess, something along the lines of not being good enough or being a failure because you haven't "achieved anything" on some timescale.
A belief like that is emotionally very close to holding a gun to your own head and telling yourself it might shoot if ...
The empty meaningless feeling is a way to turn the fear off, so you can recover. However, it turns off everything, both the fear and anything positive as well. I suspect it's similar to the effect of some antidepressants. Some of them just turn your feelings off.
Learning to endure suffering while still trying to push yourself into action by creating suffering is not a healthy thing to do. You'll just end up creating as much suffering as you can bear (because otherwise, it loses it's effectiveness in motivating you). Especially when you rarely, if ever, give yourself a break from it.
Lately, I've been taking Solgar's Vitamin K2 (Natto Extract, so not just K2), 50 micrograms of D3 and Terra Nova's Living Multinutrient Complex that has pretty much everything (except K2 or large amounts of D3). I initially started taking this combination to see if it might make a difference for my teeth cavity. It didn't. However, I've noticed that I start feeling gradually worse if I stop taking them and taking them again fixes it in a few hours. It's a rather complete package, though, so I have no theories on which nutrients, exactly are responsible.