How to Relate to Adult Children?

I am a mother.  How can I relate to my adult child when I am suffering from Depression/Anxiety?  He called, and I thought we were talking about inconsequential things, and then wham!  He hits me verbally and asks, “What’s really up, Mom?”  He has spotted my weakness amid my casual remarks.  I assume he is keenly aware of when I am hiding my problem under a false sense of jolliness.  However, it is hard to tell the truth, because I am afraid that he might blame me for my condition.  Of course, this fear is just another manifestation of my classic negative thinking, but in this case, it puts me in a real emotional bind, because I want my son to admire me at the same time that I cannot admire myself.