DD has been sleeping pretty much all day. Since waking this am, she's been awake at most only 2.5 hours (most of which was just after waking). Should I be concerned or just let her sleep? I've tried to get her interested in something to keep her alert and awake for at least a little bit, but had no success.

She's nursed only 4 times since waking up this am for only 35 minutes total. She is a super efficient eater though, typically averaging only 7 minutes or so per session.

A little background on DD...She is six weeks old and has had really inconsistent sleeping habits so far. Up until a week back, she'd sleep the vast majority of the day - from what I heard from other moms, more than their babies did at this age. Then last week, she finally started becoming much more alert with longer awake periods and shorter naps. With the exception of a few nights, night sleep has still not been great.