Hey Teeki what you wrote reminded me - and I'd completely forgotten until now - but when DD was a newborn I felt really down, quite depressed and teary actually, from about 4pm. Every day at the same time. Are you breastfeeding? For me I put it down to the basics of overwrought hormones and simply it being the end of a very long and exhausting day, but also breastmilk levels thus hormones being at their 24 hour low point. Baby is still so new and though not your first, every experience of mothering a newborn is exhausting no matter how much practice you've had!