Grace, what you described - feeling so down it's physically agonizing but not even being able to care about suicide - is what I experience now when I have a severe depressive episode. And I cannot take antidepressants because I have really negative reactions (mental and physical) to them, regardless of what class they are in. I don't really know what to tell you because obviously there is no easy answer. For me, the only thing that works is literally just taking it one day at a time. The timer suggestion is a good one; I've never heard that before. But for me, when things get really tough and I literally cannot deal, I have to tune out. I have to shut it down. I accomplish this by either surrounding myself with people (or one person) who understands and spending time with them because it always gets me outside of myself; or, if I'm too unwell to even do that, I tune out with movies or tv shows (online, without the commercials, like with Netflix or something). In fact I've had entire weeks where that's all I've done: stayed in my pjs, watched shows, and zoned out. The pain is still there, but the stimulus gives my brain something else to focus on and I become a little more desensitized to it, and then eventually it becomes more bearable again. When it gets bad enough, I go to the emergency room, because although the thought of suicide usually scares me to the point of feeling paralyzed when I contemplate it, I have attempted it in the past, and I don't really want to die; I just want the pain to stop.

I suggest experimenting and finding things that work for you, ideally more than one, and developing a 'tool box' of sorts.