sleep, or lack of...

For several months now, Luz has been sleeping more irregularly than usual. Waking up several times, sometimes crying unconsolably, sometimes going back to sleep right away, once we've come to her to snug her back to bed (she will otherwise stay sitting up, waiting for us).A couple of weeks ago we started treatment with melatonin. For the moment, this helps her to fall a sleep at a decent time, but she's still waking up several times per night (ranging from twice a night, on rare occasions, to six times a night... not so rare).
Mom and Dad are quite tired by now, and she seems undisturbed!