SO won't go to the Dr. & it's serious!

My significant other (SO) is SERIOUSLY depressed. He wakes up every morning incredibly depressed. In four years I've only seen him cry a few times and he cries every morning before he goes to work. I ask if it is work and he says he doesn't know why he is depressed. He's in his late 30's so I'm concerned maybe his testosterone has dropped. He just started a new job so his insurance hasn't kicked in yet and money has been tight so I think he is worried about the cost of going to a doctor, and I know his pride gets in the way. I would give up ANYTHING for him to be happy again. He used to be such a morning person - singing out of tune and dancing around every morning. It used to annoy me a little because I get up for work later than he does and he would wake me up being all chipper and loud. Now, I would give my left hand for him to annoy me with his singing and dancing in the morning. He barely makes a peep, mopes around with this awful, sad look on his face. He rarely smiles anymore. How do I get him to see a doctor? I've worked in a field that deals with this kind of thing for a long time. I know depression when I see it - real depression, not "my life isn't perfect" depression. This is "I'm a failure and my life is worthless" depression - clinical depression. I feel helpless. I need help knowing how to talk to him about seeking medical attention.