Depression?

I need some help! I recently have ended a relationship with someone I really cared about. We ended in very bad terms. I've been very depressed because I work with him daily. I want to tell my boss that I need to take a break from work because of my depression. How can I approach my boss about this? Working with the guy I ended bad with has been tearing me apart. Each day I keep on getting worse. I've decided that I need to get help, but I need to stop working. How can I tell my boss this?