Thanks, Harmony, for your input.

I'm so much better today, having slept well last night. I will call my pdoc if I continue to have these insomnia/depressed symptoms in the future. Still, even on meds, getting upset is a normal experience. The crying doesn't concern me so much as the insomnia/down mood.
Bummer about your kidney problems. Did you have them already, or did the lithium cause it?
About the Lexapro, my pdoc added lithium to it after my tdoc felt I needed something more. My pdoc prescribed 600mg lithium to go with the 10mg Lexapro. I would only take 300mg, being rather weirded out by the things my engineer husband would say - "Lithium? That's a light metal. You know - lithium batteries?" and such... Then I'd go off the Lexapro, and do just 300mg lithium, and vice-versa. I tried going off both and that was a disaster. So back onto Lexapro, and doing "OK"(not always emotionally stable, but able to function most days.) Then I entered a lovely state of both depressed and hypomanic symptoms this summer, either at the same time or ultra-rapid cycling (I can't remember) and called him in desperation. He added 600mg lithium to the 10mg Lexapro, and this time I took the whole amount every day. Within 5 days, I noticed a difference. By 2 weeks, I was feeling myself again. I think he'd be fine with my dropping Lexapro as long as I was doing well. If I struggle again, I'll ask him about it.
For now, I'm just seeing what 600mg lithium alone will do for me. I just wonder how others do on it alone. I fear that Lexapro brought on my summer-time hypomanic symptoms, and that's what I hope to avoid by not taking it with lithium.
It's a roller-coaster ride, isn't it?