Functionally unfunctional-when is it ok to be unfunctional enough to take care of myself?

I've been functionally unfunctional living with severe CPTSD for decades. There are a number of reasons for this for me but up until recently the functional is beginning to crack. I'm in therapy and the ruminations are less but I still cry a lot, feel exhausted, immense shame and guilt and emotional turmoil. My body still sometimes dissociates. I stare off into space a lot at work and just sit for minutes or hours thinking about the big T traumas, crying and grieving, hiding in the basement to sob in a dark corner. I can hardly focus, it's incredibly challenging and what used to take hours to complete now takes days. I think about suicide every single day and not because I don't believe it can't get better but because it's simply the most appealing future outcome I can imagine. I participate in a large way with society while I'm working but at home I'm being abused and my physical pain worsens as I age. Life is like a narrow tunnel around me that is suffocating me slowly to death and I am just tired of performing.

I've done A LOT of self care over the years btw, so I'm no stranger to that. I just have no energy left to commit to it like I once did. I feel like I've given up...

When is it ok to be unfunctional? My obligations to others overrides my needs. If I don't do this the guilt eats me alive. When is it time for me to let go for a while to take care of myself? I can't even imagine not working. I think I'd crack up without it frankly. In some ways it's the only daily distraction and reprieve but in other ways its more of the same self abandonment by pushing through under already great pressure. I'm self employed so unemployment isn't an option...