Ugh. Late nights with babies (and toddlers and preschoolers) are tough. It's so hard to know what's going on with them sometimes, especially before they can talk. Sometimes my daughter would have some rough nights in the days before she made some big developmental leap.
One thing in your description jumped out at me though, which is that your baby cried every time you put her down but talked when you picked her up. That reminds me very much of how my daughter was in infancy the first time she had an undiagnosed ear infection. It can be hard to know when a baby has an ear infection without a doctor visit since babies don't usually pull at their ears when they hurt, and sometimes they don't run a fever. We only discovered it because my daughter participated in a research study at the university where they were testing her response to auditory stimuli. One of the measures they took was ear pressure, and the person conducting the experiment happened to mention hers wasn't normal. (She also kept pulling the earpiece out of her ear because it was uncomfortable.) I took her to the doctor and, lo and behold, she had a raging ear infection.
What my husband and I noticed in retrospect was that she was having trouble staying asleep. Apparently, kids' ears hurt more when they're lying down and the pain can wake them up. She's still the same way now, at age 3 1/2. I can tell she's got an ear infection when she fusses about lying down or keeps waking up all night.
There are innumerable reasons babies don't sleep well, of course, so it could be anything, but I just thought I should mention it in case it can save you some sleepless hours.
Jenny
