Therapists typically (NOT always) will work with you confidentially about suicidal ideations (thoughts, feelings, wishes) but will very often report suicidal plans due to legal liability to prevent you from harming yourself, of course, along with their understandable human desire to keep you safe.

As for other secrets, they'll keep those confidential as long as they don't involve a clear threat or real harm to yourself or others, things like that.

You can ask your therapist their policy to feel it out first, also make sure you work with someone experienced, licensed, recommended or carefully researched and familiar with your issues to minimize chances of harm.

Very sorry you're struggling with this.

As for me personally, yes, I've talked about suicide with my therapist more than once. She listened closely and was supportive. She did ask me in a couple separate instances if I was actively suicidal, i.e. if I had a plan, and it was clear to me that a yes answer would have meant she escalated the issue. I did not have a plan and answered honestly that I was feeling suicidal, not planning it. That's as far as it's gotten with me, but I know many others here may have more insight for you.

As for having bad things happen- yes, when I was 16 I saw a therapist and was dealing with past abuse. She was worried about me and broke confidentiality, talking with my mother and reading a journal my mother found and gave her. That was horrific for me, wrenching, a period of terrible anxiety and upset. That counselor was only an intern, not too experienced and I was not a good consumer then. I feel much safer as an adult working with a much more qualified therapist.