I've told him everything, but...

I've been with my boyfriend for a year. We are very open and honest with each other, and don't hesitate to say what we're thinking. However, there is one thing I've never told him about... I'm diagnosed with clinical depression, and I'm plagued with constant thoughts of harming myself. With age, I've learned to cope, and taught myself to no longer act upon these thoughts, but I still think about them everyday. I want to open up the conversation, and tell my significant other about this because he deserves to know, but I don't want him to worry. I know that I won't harm myself, I am safe, I am okay, I want to be alive, I'm just not sure that he would understand that. I don't want him to live in constant fear of me relapsing and causing myself any harm. Any advice on how to open up the dialogue on this?