How do explain my depression to my new boyfriend?

We’ve been dating for a few months now; things have been good, and I’ve been healthy and happy so far. I’m kind of in a bad place all of the sudden (feeling crazy about the election, hopeless about the state of the world and my future, plus some big job disappointments), and I feel like he doesn’t really get why I feel so down. He knows I take anti-depressants and anti-anxiety medicine, but I’ve never tried to explain why I do, or anything about my history with depression. My last relationship failed partly because my ex just didn’t understand why I couldn’t make myself happy, no matter how many times I tried to tell him. So how do I do things different this time? How do I make him understand what I’m feeling? He’s always optimistic, incredibly successful in his field, tall, handsome, flawless…sometimes I wonder if anything bad has ever, ever happened to him. He knows something’s up because I’ve been on crying jags and really moody, but I don’t know how to explain to him that I’m at the bottom of a hole right now and climbing out, but that it’ll probaby take a while.Help?