I do know a way you can talk about that subject without having to say you yourself are depressed and self-harming. You simply ask questions, such as:
"Have you ever been depressed, mom?"
She'll probably say yes, and perhaps describe what her experience was like. This could help you two stand on common ground if you find out if she understands the feeling of anxiety/depression, or at least somewhat of it. Though I'm 102% sure she would know what depression feels like. Most of us have been there.
Just make sure the questions are directed at her, so she can answer with her own opinion on the matter. Eventually she may ask about how you feel, and from then on I hope you became more comfortable with talking about it with your mother.
Believe me, you don't have depression. It's just something that you think is depression. And about the thing, about talking with your mom, just start simple. Talk to her about small things. Then while in conversation, just tell her about how you are feeling. I'm sure she will listen to you and try to help if you talk to her calmly. You just need to take 3 deep breaths and go talk to your mother. She's your mother for God sakes. She knows the best. Just go and talk to her.