How would you explain this feeling, especially to your therapist?

Bare with me, I’m struggling putting it into words, but I’m excited to see how you view it/would explain it to your therapist cause what I have so far doesn’t feel enough or explain it well enough You know that feeling of sadness + crushing + being consumed when you’re having a low but it’s a real real bad low that feels like the end of the world. It’s kinda like the world is falling apart and you manage to feel every single bit of it in a way. It’s a gigantic low that really only borderlines can feel. You just want to die then and there and you wouldn’t even really wish it upon your worst enemy when you’re baseline/close to baseline. Sorry if that’s not helpful I’m struggling to find the words to explain it