Feel free to move this post if there's a better place for it, I'm not entirely sure where to put it...

So my two best friends found out that I SI and are saying if I don't tell my parents by Wednesday, they'll come over and tell them. I have a lot of trust issues with my parents, but at this point I understand I just need to tell them everything that is going on because mental health issues are just piling up.

I need help on multiple things because I'm not all that experienced in telling people my issues

1) I cry every time I talk about something personal. I know that when I tell them I'll lose a lot of my "credibility," I guess, by crying and not being able to straight up tell them what's going on. I've been told before by both of my parents that crying is just seeking self-pity, so even if I don't believe that I'd rather have them take me seriously. How can I talk to them and stay calm?

2) How do I bring it up? I've come so close to telling them in the past but I never know how to start the conversation. I'd rather do it in a secluded place because I have younger siblings who I'd rather not have exposed to a lot of what I'm going to tell my parents. I'm not sure whether or not I want to tell both or just one, but I'm not sure that's relevant.

3) When should I talk to them? My second major struggle with talking to them is finding the perfect moment when they aren't angry with me, stressed/grumpy, or overly proud of me. The last time we talked about mental illness (when my mom found a narrative essay I had written for school), she was supportive, but I could tell it stressed her out and that she really didn't believe I had any actual illness. This makes it hard for me to know when to reach out and when she will believe me.

Thank you all for your time and I'd be happy for any of these answered soon so I can not procrastinate. I would be okay with half-answers or answers for specific questions, I don't really care. I just need as much information as I can before moving forward

I love you all and thanks for being continually supportive