Other
It's a combination of factors, and it's complicated. There isn't just one primary reason. Here are the top 3:
I have a cancer history, and I'm driving myself crazy waiting for the other shoe to drop. I'm apparently so afraid of dying, I'd rather just die already.
I lost the only future I ever really wanted, and I'm not able to accept that and make a new one. I want exactly what I lost, not something different.
One day, my brain just randomly decided I need to die, and I can't seem to convince myself otherwise. I have things to live for, but I am plagued with almost obsessive thoughts and urges to end myself. It's exhausting, and I'm sick of fighting it.