How do I tell my mom I've been self harming? She knows I have depression and that I tried ending my life before. I just am having a hard time sharing.

Sometimes it can be helpful to just write down that this is going on, especially if it's hard for you to get the words out, or you can sit down with her and have a heart to heart explain to her what is going on and being opened and honest

Wanting to tell your mother about your self-harming shows that you see her as someone you can trust with understanding the kind of pain that you're going through right now. Since she knows about your depression and past attempt at suicide, she might be so grateful that you are giving her the opportunity to support you during this tough time. Please know that there are people who will always want to hear what you have to say, or know about how you are feeling. There are many people who want to love you and give you the care that you deserve, so please try to give them that chance. Your mom would be happy to be one of them.