For me this death urge was between age seven up to age, maybe 25, 26 or so. And then a new stretch between say 32 and 35. Really glad I didn't KMS. I went through a really long time of wanting to die. So grateful I didn't. It's less "it gets better" and more "it's possible to learn to appreciate what's there".
And by appreciate I mean really treasure everyday life. I can get nearly ecstatic from just a plain glass of water or a nice stone floor. Pretty happy I'm not missing out on that.
This isn't to gloat, just to give hope.
It's difficult but possible. I hope you find the resources and the help to guide you towards the meaning or the acceptance you need.