Can relate very very well. I have one person I could never keep myself from telling and it always resulted in me essentially being stopped. But honestly, truly honestly, I think I always told her because deep down I wanted her to stop me. I wanted to die. I still do. But I wanted someone to say "hey, you're worth being here, you need to hold on longer, if not for your sake then for mine." I feel awful for putting her through so much but in the end she really has kept me alive. Honestly.
We stopped talking and I planned suicide again. This time it was no doubt I'd do it. I didn't feel the urge to tell ANYONE, because she's the only one I'd ever tell, and we weren't talking. I became content with dying alone. Dying was an easy choice without her in the picture.
Then she re-entered my life and I'm back to being a burdensome suicidal piece of shit. If she hadn't messaged me I'd be dead hopefully by the end of this month. I might still be. But it's enormously difficult to not tell her where my head is at. I trust her and find immense comfort in her. It's so nice to not feel alone.
Anyways. This is just where I'm at. I'm not answering your question at all, just trying to relate to your situation. It's a selfish soap box. Sorry for that. I'm just emotional right now. I want to die, and could easily die, I have my SN and etc, but can't stop from telling her. If I drank it I'm frankly like 80% sure I'd immediately tell her what I've done and it would be 1. a failed/aborted attempt and 2. a repeat of all the other times I've hurt her over my self loathing. I should go to bed.