Why the hell was she screaming all night?

Thank goodness last night was back to normal, because the night before sucked. Carter nursed then screamed, nursed then screamed, nursed then screamed, then just screamed and screamed for 45 min. No idea what was wrong. Tried more nursing, patting, singing, walking, bringing the baby swing back up out of the basement, sitting up in a chair, rocking....and on and on. Rocking while singing was the only thing that even made her temporarily quiet. No clue what was wrong. And by this time it was midnight and Drew and I were starting to go batty. Thank God I finally thought of her music class CD that pacifies her in the car. We brought it up and she laid awake in my arms and listened to it and finally drifted off after 30 min. Drew and I dozed off the minute she shut up I think, we were so tired. But she was eventually asleep before the CD ended because I woke up to turn it off. Or have Drew turn it off rather, since she was sleeping on my left arm. But at least she was asleep. And not screaming--that was the key!