DD has always been a brilliant sleeper. She sleeps 12-13 hours per night. Over the past week she has been crying in the night (we leave her and she then will re-settle), and waking at 7am (after 10 hours sleep) rather than 9am, as she previously did. When she wakes she screams, and is hysterical by the time we get to her. I seem to remember her having these phases before but I always worry....is this likely another phase? Why is she suddenly waking throughout the night and so early in the morning?