My son is almost 6 months old, and is a pretty good sleeper for the most part. For the past few nights, though, he wakes about one hour into the evening and screams at the top of his lungs. By this point I know all of his different types of cries-this cry is one unlike anything I've ever heard. It sounds like he's experiencing a horrible pain and he isn't immediately soothed by nursing-which typically cures anything. Could this be a sign of teething? Is there something developmental I'm missing? He's not hungry and has a fresh diaper, so I know neither of those is the culprit. After 15-20 minutes we can often get him back to sleep by rocking, nursing, back pats, etc., but before then he just shrieks. However, we'd love to figure out what a cause might be-if there is one.